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String Interview Questions

Master 698 string problems frequently asked in technical interviews. These questions test your understanding of stringconcepts and are essential for coding interview success.

698

Total Problems

197

Easy

348

Medium

153

Hard

Related Topics

Hash Table Array Dynamic Programming Greedy Math Two Pointers Counting Sorting

#1371MediumFrequency: 100%

Minimum Remove to Make Valid Parentheses

#1

Rank

#68HardFrequency: 100%

Text Justification

Asked at Airbnb

Array String Simulation

#2

Rank

#6MediumFrequency: 100%

Zigzag Conversion

Asked at PayPal

#3

Rank

#752MediumFrequency: 97.6%

IP to CIDR

Asked at Databricks

String Bit Manipulation

#4

Rank

#408EasyFrequency: 96.8%

Valid Word Abbreviation

Two Pointers String

#5

Rank

#269HardFrequency: 95.2%

Alien Dictionary

Array String Depth-First Search Breadth-First Search Graph Theory Topological Sort Directed Acyclic Graph

#6

Rank

#680EasyFrequency: 95.1%

Valid Palindrome II

Two Pointers String Greedy

#7

Rank

#3MediumFrequency: 92.8%

Longest Substring Without Repeating Characters

Asked at Infosys

Hash Table String Sliding Window

#8

Rank

#227MediumFrequency: 89.3%

Basic Calculator II

Math String Stack

#9

Rank

#443MediumFrequency: 88.1%

String Compression

Asked at Salesforce

Two Pointers String

#10

Rank

#438MediumFrequency: 84.4%

Find All Anagrams in a String

Asked at Databricks

Hash Table String Sliding Window

#11

Rank

#71MediumFrequency: 83.7%

Simplify Path

#12

Rank

#2217MediumFrequency: 83.7%

Step-By-Step Directions From a Binary Tree Node to Another

Asked at Databricks

String Tree Depth-First Search Binary Tree Binary Lifting Lowest Common Ancestor

#13

Rank

#1112EasyFrequency: 82.7%

Find Words That Can Be Formed by Characters

Asked at PayPal

Array Hash Table String Counting

#14

Rank

#125EasyFrequency: 82.6%

Valid Palindrome

Two Pointers String

#15

Rank

#1397MediumFrequency: 82.5%

Search Suggestions System

Asked at DoorDash

Array String Binary Search Trie Sorting Heap (Priority Queue)

#16

Rank

#1190MediumFrequency: 82.4%

Smallest Common Region

Asked at Airbnb

Array Hash Table String Tree Depth-First Search Breadth-First Search Binary Lifting Lowest Common Ancestor

#17

Rank

#244MediumFrequency: 82.3%

Shortest Word Distance II

Asked at LinkedIn

Array Hash Table Two Pointers String Design

#18

Rank

#49MediumFrequency: 81.6%

Group Anagrams

Asked at Oracle

Array Hash Table String Sorting

#19

Rank

#564HardFrequency: 80.8%

Find the Closest Palindrome

#20

Rank

#2691MediumFrequency: 80.7%

Count Vowel Strings in Ranges

Asked at PayPal

Array String Prefix Sum

#21

Rank

#5MediumFrequency: 80.5%

Longest Palindromic Substring

Asked at Microsoft

Two Pointers String Dynamic Programming Manacher

#22

Rank

#1023MediumFrequency: 79.9%

Time Based Key-Value Store

Asked at Databricks

Hash Table String Binary Search Design

#23

Rank

#2464MediumFrequency: 79.6%

Time Needed to Rearrange a Binary String

Asked at Salesforce

String Dynamic Programming Simulation

#24

Rank

#20EasyFrequency: 79%

Valid Parentheses

Asked at LinkedIn

String Stack Bracket Sequences

#25

Rank

#127HardFrequency: 79%

Word Ladder

Asked at LinkedIn

Hash Table String Breadth-First Search Bidirectional Search

#26

Rank

#336HardFrequency: 78.6%

Palindrome Pairs

Asked at Airbnb

Array Hash Table String Trie Hash Function

#27

Rank

#631HardFrequency: 78.6%

Design Excel Sum Formula

Asked at Airbnb

Array Hash Table String Graph Theory Design Topological Sort Matrix

#28

Rank

#778MediumFrequency: 78.3%

Reorganize String

Asked at Amazon

Hash Table String Greedy Sorting Heap (Priority Queue)Counting

#29

Rank

#79MediumFrequency: 78%

Word Search

Array String Backtracking Depth-First Search Matrix

#30

Rank

#2147HardFrequency: 76.6%

The Score of Students Solving Math Expression

Asked at Flipkart

Array Hash Table Math String Dynamic Programming Stack Memoization

#31

Rank

#14EasyFrequency: 76.4%

Longest Common Prefix

Array String Trie

#32

Rank

#394MediumFrequency: 75.8%

Decode String

Asked at TikTok

String Stack Recursion

#33

Rank

#76HardFrequency: 74.7%

Minimum Window Substring

Asked at TikTok

Hash Table String Sliding Window

#34

Rank

#17MediumFrequency: 73.6%

Letter Combinations of a Phone Number

Asked at LinkedIn

Hash Table String Backtracking

#35

Rank

#212HardFrequency: 73.4%

Word Search II

Array String Backtracking Trie Matrix

#36

Rank

#2166HardFrequency: 73.2%

Number of Valid Move Combinations On Chessboard

Asked at PayPal

Array String Backtracking Simulation

#37

Rank

#2654EasyFrequency: 73.2%

Count the Number of Vowel Strings in Range

Asked at PayPal

Array String Counting

#38

Rank

#807MediumFrequency: 72.8%

Custom Sort String

Hash Table String Sorting

#39

Rank

#1125MediumFrequency: 72.7%

Design File System

Asked at DoorDash

Hash Table String Design Trie

#40

Rank

#957MediumFrequency: 71.8%

Minimum Add to Make Parentheses Valid

String Stack Greedy Bracket Sequences

#41

Rank

#3706HardFrequency: 71.5%

Smallest Substring With Identical Characters II

Asked at Salesforce

String Binary Search

#42

Rank

#399MediumFrequency: 70.2%

Evaluate Division

Array String Depth-First Search Breadth-First Search Union-Find Graph Theory Shortest Path Bellman–Ford Algorithm Floyd–Warshall Algorithm

#43

Rank

#242EasyFrequency: 69.8%

Valid Anagram

Asked at Infosys

Hash Table String Sorting

#44

Rank

#1894EasyFrequency: 69.5%

Merge Strings Alternately

Asked at Google

Two Pointers String

#45

Rank

#13EasyFrequency: 69.2%

Roman to Integer

Asked at Microsoft

Hash Table Math String

#46

Rank

#22MediumFrequency: 69.1%

Generate Parentheses

Asked at Amazon

String Dynamic Programming Backtracking Bracket Sequences

#47

Rank

#65HardFrequency: 68.2%

Valid Number

#48

Rank

#151MediumFrequency: 68%

Reverse Words in a String

Two Pointers String

#49

Rank

#3356MediumFrequency: 67.9%

Shortest Uncommon Substring in an Array

Asked at Airbnb

Array Hash Table String Trie

#50

Rank

#3230MediumFrequency: 67.8%

Remove Adjacent Almost-Equal Characters

Asked at Salesforce

String Dynamic Programming Greedy

#51

Rank

#785HardFrequency: 66.8%

Basic Calculator III

Asked at TikTok

Math String Stack Recursion

#52

Rank

#1304MediumFrequency: 66.8%

Longest Happy String

Asked at TikTok

String Greedy Heap (Priority Queue)

#53

Rank

#1423MediumFrequency: 66.4%

Maximum Number of Occurrences of a Substring

Asked at Salesforce

Hash Table String Sliding Window

#54

Rank

#3317MediumFrequency: 66.4%

Maximum Palindromes After Operations

Asked at Salesforce

Array Hash Table String Greedy Sorting Counting

#55

Rank

#588HardFrequency: 65.6%

Design In-Memory File System

Asked at DoorDash

Hash Table String Design Trie Sorting

#56

Rank

#889EasyFrequency: 65.6%

Buddy Strings

Asked at DoorDash

Hash Table String

#57

Rank

#10HardFrequency: 65.5%

Regular Expression Matching

Asked at Airbnb

String Dynamic Programming Recursion

#58

Rank

#1053MediumFrequency: 65.5%

Minimize Rounding Error to Meet Target

Asked at Airbnb

Array Math String Greedy Sorting

#59

Rank

#385MediumFrequency: 65.5%

Mini Parser

Asked at Airbnb

String Stack Depth-First Search

#60

Rank

#415EasyFrequency: 65.5%

Add Strings

Asked at Airbnb

Math String Simulation

#61

Rank

#1119MediumFrequency: 65.5%

Robot Bounded In Circle

Asked at Airbnb

Math String Simulation

#62

Rank

#1697MediumFrequency: 65.5%

Strings Differ by One Character

Asked at Airbnb

Hash Table String Rolling Hash Hash Function

#63

Rank

#757MediumFrequency: 65.5%

Pyramid Transition Matrix

Asked at Airbnb

Hash Table String Backtracking Bit Manipulation

#64

Rank

#556MediumFrequency: 64.6%

Next Greater Element III

Asked at DoorDash

Math Two Pointers String

#65

Rank

#1915EasyFrequency: 64.6%

Check if One String Swap Can Make Strings Equal

Asked at DoorDash

Hash Table String Counting

#66

Rank

#1320MediumFrequency: 63.5%

Remove All Adjacent Duplicates in String II

Asked at Oracle

#67

Rank

#1469MediumFrequency: 63.5%

Minimum Number of Steps to Make Two Strings Anagram

Asked at DoorDash

Hash Table String Counting

#68

Rank

#678MediumFrequency: 63.4%

Valid Parenthesis String

Asked at TikTok

String Dynamic Programming Stack Greedy Bracket Sequences

#69

Rank

#297HardFrequency: 63.4%

Serialize and Deserialize Binary Tree

Asked at LinkedIn

String Tree Depth-First Search Breadth-First Search Design Binary Tree

#70

Rank

#115HardFrequency: 63.3%

Distinct Subsequences

Asked at Salesforce

String Dynamic Programming

#71

Rank

#647MediumFrequency: 63%

Palindromic Substrings

Two Pointers String Dynamic Programming

#72

Rank

#1108MediumFrequency: 62.6%

Analyze User Website Visit Pattern

Asked at Amazon

Array Hash Table String Sorting

#73

Rank

#205EasyFrequency: 62.6%

Isomorphic Strings

Asked at LinkedIn

Hash Table String

#74

Rank

#2077MediumFrequency: 62.5%

Largest Number After Mutating Substring

Asked at Infosys

Array String Greedy

#75

Rank

#2502EasyFrequency: 62.5%

Sort the People

Asked at Infosys

Array Hash Table String Sorting

#76

Rank

#1647MediumFrequency: 62.5%

Can Convert String in K Moves

Asked at Infosys

Hash Table String

#77

Rank

#224HardFrequency: 61.8%

Basic Calculator

Math String Stack Recursion

#78

Rank

#243EasyFrequency: 61.6%

Shortest Word Distance

Asked at LinkedIn

#79

Rank

#249MediumFrequency: 61.4%

Group Shifted Strings

Array Hash Table String

#80

Rank

#721MediumFrequency: 61.4%

Accounts Merge

Array Hash Table String Depth-First Search Breadth-First Search Union-Find Sorting

#81

Rank

#851EasyFrequency: 61.1%

Goat Latin

#82

Rank

#2237MediumFrequency: 61.1%

Longest Palindrome by Concatenating Two Letter Words

Asked at Databricks

Array Hash Table String Greedy Counting

#83

Rank

#139MediumFrequency: 60.5%

Word Break

Array Hash Table String Dynamic Programming Trie Memoization Brute-Force Search

#84

Rank

#3736EasyFrequency: 60%

Find Valid Pair of Adjacent Digits in String

Asked at Oracle

Hash Table String Counting

#85

Rank

#424MediumFrequency: 59.8%

Longest Repeating Character Replacement

Asked at Amazon

Hash Table String Sliding Window

#86

Rank

#1298MediumFrequency: 59.8%

Reverse Substrings Between Each Pair of Parentheses

Asked at Flipkart

String Stack Bracket Sequences

#87

Rank

#1341EasyFrequency: 59.6%

Split a String in Balanced Strings

Asked at Salesforce

String Greedy Counting

#88

Rank

#2337EasyFrequency: 59.4%

Remove Digit From Number to Maximize Result

Asked at Infosys

String Greedy Enumeration

#89

Rank

#72MediumFrequency: 59.3%

Edit Distance

Asked at TikTok

String Dynamic Programming

#90

Rank

#140HardFrequency: 59.3%

Word Break II

Asked at TikTok

Array Hash Table String Dynamic Programming Backtracking Trie Memoization

#91

Rank

#3638HardFrequency: 59.3%

Minimum Operations to Make Character Frequencies Equal

Asked at TikTok

Hash Table String Dynamic Programming Counting Enumeration

#92

Rank

#3701HardFrequency: 59.3%

Minimum Cost Good Caption

Asked at TikTok

String Dynamic Programming

#93

Rank

#3770HardFrequency: 59.3%

Lexicographically Smallest Generated String

Asked at TikTok

String Greedy String Matching

#94

Rank

#692MediumFrequency: 59.1%

Top K Frequent Words

Array Hash Table String Trie Sorting Heap (Priority Queue)Bucket Sort Counting

#95

Rank

#282HardFrequency: 58.8%

Expression Add Operators

Math String Backtracking

#96

Rank

#1178HardFrequency: 57.8%

Valid Palindrome III

String Dynamic Programming

#97

Rank

#187MediumFrequency: 57.5%

Repeated DNA Sequences

Asked at LinkedIn

Hash Table String Bit Manipulation Sliding Window Rolling Hash Hash Function Z Algorithm Boyer–Moore String-Search Algorithm

#98

Rank

#763HardFrequency: 57.5%

Special Binary String

Asked at Salesforce

String Divide and Conquer Sorting

#99

Rank

#1434EasyFrequency: 57.5%

Decrypt String from Alphabet to Integer Mapping

Asked at Salesforce

#100

Rank

#8MediumFrequency: 57.3%

String to Integer (atoi)

#101

Rank

#1308MediumFrequency: 57%

Smallest String With Swaps

Asked at PayPal

Array Hash Table String Depth-First Search Breadth-First Search Union-Find Sorting

#102

Rank

#516MediumFrequency: 56.3%

Longest Palindromic Subsequence

Asked at LinkedIn

String Dynamic Programming

#103

Rank

#2563HardFrequency: 55.9%

Split Message Based on Limit

String Enumeration

#104

Rank

#2594EasyFrequency: 55.8%

Count Pairs Of Similar Strings

Asked at Oracle

Array Hash Table String Bit Manipulation Counting

#105

Rank

#4071MediumFrequency: 55.8%

Word Squares II

Asked at Oracle

Array String Backtracking Sorting Enumeration

#106

Rank

#1128EasyFrequency: 55.6%

Remove All Adjacent Duplicates In String

#107

Rank

#387EasyFrequency: 55.2%

First Unique Character in a String

Asked at Amazon

Hash Table String Queue Counting

#108

Rank

#28EasyFrequency: 55.2%

Find the Index of the First Occurrence in a String

Asked at Microsoft

Two Pointers String String Matching Z Algorithm Knuth–Morris–Pratt Algorithm Boyer–Moore String-Search Algorithm

#109

Rank

#2177EasyFrequency: 55.1%

Check Whether Two Strings are Almost Equivalent

Asked at Salesforce

Hash Table String Counting

#110

Rank

#3433MediumFrequency: 55.1%

Maximum Number That Makes Result of Bitwise AND Zero

Asked at Salesforce

String Greedy Sorting

#111

Rank

#3441MediumFrequency: 55.1%

Equalize Strings by Adding or Removing Characters at Ends

Asked at Salesforce

String Binary Search Dynamic Programming Sliding Window Hash Function

#112

Rank

#1250MediumFrequency: 55.1%

Longest Common Subsequence

Asked at Salesforce

String Dynamic Programming Longest Common Subsequence

#113

Rank

#165MediumFrequency: 55%

Compare Version Numbers

Two Pointers String

#114

Rank

#208MediumFrequency: 55%

Implement Trie (Prefix Tree)

Hash Table String Design Trie

#115

Rank

#383EasyFrequency: 55%

Ransom Note

Hash Table String Counting

#116

Rank

#316MediumFrequency: 54.4%

Remove Duplicate Letters

Asked at TikTok

String Stack Greedy Monotonic Stack

#117

Rank

#2492MediumFrequency: 54.4%

Length of the Longest Alphabetical Continuous Substring

Asked at TikTok

#118

Rank

#2543MediumFrequency: 54.4%

Most Popular Video Creator

Asked at TikTok

Array Hash Table String Sorting Heap (Priority Queue)

#119

Rank

#211MediumFrequency: 54.4%

Design Add and Search Words Data Structure

Asked at TikTok

String Depth-First Search Design Trie

#120

Rank

#3613MediumFrequency: 54.1%

Maximize Amount After Two Days of Conversions

Array String Depth-First Search Breadth-First Search Graph Theory

#121

Rank

#67EasyFrequency: 53.4%

Add Binary

Asked at Google

Math String Bit Manipulation Simulation

#122

Rank

#93MediumFrequency: 53.4%

Restore IP Addresses

Asked at Oracle

String Backtracking

#123

Rank

#1526MediumFrequency: 53.4%

HTML Entity Parser

Asked at Oracle

Hash Table String

#124

Rank

#3732MediumFrequency: 53.1%

Calculate Score After Performing Instructions

Array Hash Table String Simulation

#125

Rank

#472HardFrequency: 53%

Concatenated Words

Asked at Amazon

Array String Dynamic Programming Depth-First Search Trie Sorting

#126

Rank

#12MediumFrequency: 52.8%

Integer to Roman

Asked at Microsoft

Hash Table Math String

#127

Rank

#273HardFrequency: 52.8%

Integer to English Words

Asked at Microsoft

Math String Recursion

#128

Rank

#567MediumFrequency: 52.8%

Permutation in String

Asked at Microsoft

Hash Table Two Pointers String Sliding Window

#129

Rank

#91MediumFrequency: 52.1%

Decode Ways

String Dynamic Programming

#130

Rank

#648MediumFrequency: 52.1%

Replace Words

Array Hash Table String Trie

#131

Rank

#32HardFrequency: 51.7%

Longest Valid Parentheses

String Dynamic Programming Stack Bracket Sequences

#132

Rank

#179MediumFrequency: 51.4%

Largest Number

Asked at Amazon

Array String Greedy Sorting

#133

Rank

#395MediumFrequency: 51.4%

Longest Substring with At Least K Repeating Characters

Asked at TikTok

Hash Table String Divide and Conquer Sliding Window

#134

Rank

#1146EasyFrequency: 51.4%

Greatest Common Divisor of Strings

Asked at TikTok

Math String Euclidean Algorithm Greatest Common Divisor

#135

Rank

#2701HardFrequency: 51.3%

Subsequence With the Minimum Score

Asked at DoorDash

Two Pointers String Binary Search

#136

Rank

#245MediumFrequency: 50.6%

Shortest Word Distance III

Asked at LinkedIn

#137

Rank

#246EasyFrequency: 50.5%

Strobogrammatic Number

Hash Table Two Pointers String

#138

Rank

#131MediumFrequency: 50.4%

Palindrome Partitioning

Asked at Amazon

String Dynamic Programming Backtracking

#139

Rank

#2186EasyFrequency: 50.3%

Count Vowel Substrings of a String

Asked at PayPal

Hash Table String

#140

Rank

#301HardFrequency: 50.1%

Remove Invalid Parentheses

String Backtracking Breadth-First Search

#141

Rank

#171EasyFrequency: 49.9%

Excel Sheet Column Number

#142

Rank

#535MediumFrequency: 49.9%

Encode and Decode TinyURL

Hash Table String Design Hash Function

#143

Rank

#753MediumFrequency: 49.9%

Open the Lock

Array Hash Table String Breadth-First Search Bidirectional Search

#144

Rank

#2977EasyFrequency: 49.9%

Check if a String Is an Acronym of Words

#145

Rank

#43MediumFrequency: 49.3%

Multiply Strings

Math String Simulation

#146

Rank

#3541MediumFrequency: 49.3%

Report Spam Message

Asked at Salesforce

Array Hash Table String

#147

Rank

#257EasyFrequency: 48.7%

Binary Tree Paths

String Backtracking Tree Depth-First Search Binary Tree

#148

Rank

#2133MediumFrequency: 48.7%

Number of Pairs of Strings With Concatenation Equal to Target

Array Hash Table String Counting

#149

Rank

#812EasyFrequency: 48.1%

Rotate String

Asked at Amazon

String String Matching

#150

Rank

#340MediumFrequency: 48%

Longest Substring with At Most K Distinct Characters

Asked at TikTok

Hash Table String Sliding Window

#151

Rank

#2165MediumFrequency: 47.7%

Plates Between Candles

Asked at Amazon

Array String Binary Search Prefix Sum

#152

Rank

#536MediumFrequency: 47.5%

Construct Binary Tree from String

String Stack Tree Depth-First Search Binary Tree

#153

Rank

#161MediumFrequency: 47.5%

One Edit Distance

Two Pointers String

#154

Rank

#186MediumFrequency: 47.5%

Reverse Words in a String II

Two Pointers String

#155

Rank

#266EasyFrequency: 47.5%

Palindrome Permutation

Hash Table String Bit Manipulation

#156

Rank

#290EasyFrequency: 47.5%

Word Pattern

Hash Table String

#157

Rank

#291MediumFrequency: 47.5%

Word Pattern II

Hash Table String Backtracking

#158

Rank

#1502MediumFrequency: 47.5%

Construct K Palindrome Strings

Hash Table String Greedy Counting

#159

Rank

#2065HardFrequency: 47.5%

Check for Contradictions in Equations

Array String Depth-First Search Union-Find Graph Theory

#160

Rank

#2093EasyFrequency: 47.5%

Check If String Is a Prefix of Array

Array Two Pointers String

#161

Rank

#2099EasyFrequency: 47.5%

Number of Strings That Appear as Substrings in Word

#162

Rank

#2361EasyFrequency: 47.5%

Calculate Digit Sum of a String

String Simulation

#163

Rank

#3385MediumFrequency: 47.5%

Match Alphanumerical Pattern in Matrix I

Array Hash Table String Matrix

#164

Rank

#345EasyFrequency: 47.4%

Reverse Vowels of a String

Asked at Oracle

Two Pointers String

#165

Rank

#168EasyFrequency: 47.3%

Excel Sheet Column Title

Asked at Microsoft

#166

Rank

#583MediumFrequency: 46.7%

Delete Operation for Two Strings

Asked at Infosys

String Dynamic Programming Longest Common Subsequence

#167

Rank

#132HardFrequency: 46.7%

Palindrome Partitioning II

Asked at Infosys

String Dynamic Programming

#168

Rank

#58EasyFrequency: 46.5%

Length of Last Word

Asked at Google

#169

Rank

#44HardFrequency: 45.8%

Wildcard Matching

Asked at Microsoft

String Dynamic Programming Greedy Recursion

#170

Rank

#344EasyFrequency: 45.6%

Reverse String

Asked at Amazon

Two Pointers String

#171

Rank

#402MediumFrequency: 45.1%

Remove K Digits

Asked at Google

String Stack Greedy Monotonic Stack

#172

Rank

#2364HardFrequency: 44.8%

Longest Path With Different Adjacent Characters

Array String Tree Depth-First Search Graph Theory Topological Sort

#173

Rank

#2559HardFrequency: 44.7%

Maximum Number of Non-overlapping Palindrome Substrings

Asked at LinkedIn

Two Pointers String Dynamic Programming Greedy

#174

Rank

#730HardFrequency: 44.7%

Count Different Palindromic Subsequences

Asked at LinkedIn

String Dynamic Programming

#175

Rank

#873HardFrequency: 44.3%

Guess the Word

Asked at Google

Array Math String Minimax Interactive Game Theory

#176

Rank

#126HardFrequency: 44.1%

Word Ladder II

Asked at Amazon

Hash Table String Backtracking Breadth-First Search Bidirectional Search

#177

Rank

#938HardFrequency: 44%

Numbers At Most N Given Digit Set

Asked at TikTok

Array Math String Binary Search Dynamic Programming

#178

Rank

#392EasyFrequency: 43.3%

Is Subsequence

Two Pointers String Dynamic Programming

#179

Rank

#332HardFrequency: 43.2%

Reconstruct Itinerary

Asked at Flipkart

Array String Depth-First Search Graph Theory Sorting Heap (Priority Queue)Eulerian Circuit Eulerian Path Semi-Eulerian Graph

#180

Rank

#451MediumFrequency: 43.2%

Sort Characters By Frequency

Asked at Flipkart

Hash Table String Sorting Heap (Priority Queue)Bucket Sort Counting

#181

Rank

#726HardFrequency: 43.2%

Number of Atoms

Asked at Flipkart

Hash Table String Stack Sorting

#182

Rank

#677MediumFrequency: 43.2%

Map Sum Pairs

Asked at Flipkart

Hash Table String Design Trie

#183

Rank

#2414MediumFrequency: 42.7%

Move Pieces to Obtain a String

Asked at Google

Two Pointers String

#184

Rank

#3825MediumFrequency: 42.7%

Apply Substitutions

Asked at Google

Array Hash Table String Depth-First Search Breadth-First Search Graph Theory Topological Sort

#185

Rank

#389EasyFrequency: 42%

Find the Difference

Asked at Google

Hash Table String Bit Manipulation Sorting

#186

Rank

#412EasyFrequency: 42%

Fizz Buzz

Asked at Amazon

Math String Simulation

#187

Rank

#808MediumFrequency: 41.6%

Number of Matching Subsequences

Array Hash Table String Binary Search Dynamic Programming Trie Sorting

#188

Rank

#768MediumFrequency: 41.4%

Partition Labels

Asked at Amazon

Hash Table Two Pointers String Greedy

#189

Rank

#2547EasyFrequency: 41.2%

Odd String Difference

Asked at Salesforce

Array Hash Table String

#190

Rank

#2095MediumFrequency: 40.9%

Minimum Number of Swaps to Make the String Balanced

Asked at PayPal

Two Pointers String Stack Greedy Bracket Sequences

#191

Rank

#1967MediumFrequency: 40.9%

Longest Substring Of All Vowels in Order

Asked at PayPal

String Sliding Window

#192

Rank

#1129MediumFrequency: 40.9%

Longest String Chain

Asked at PayPal

Array Hash Table Two Pointers String Dynamic Programming Sorting

#193

Rank

#38MediumFrequency: 40.8%

Count and Say

Asked at Amazon

#194

Rank

#1170HardFrequency: 40.5%

Shortest Common Supersequence

Asked at Microsoft

String Dynamic Programming Longest Common Subsequence

#195

Rank

#793MediumFrequency: 40.2%

Swap Adjacent in LR String

Asked at Google

Two Pointers String

#196

Rank

#765HardFrequency: 39.4%

Serialize and Deserialize N-ary Tree

String Tree Depth-First Search Breadth-First Search

#197

Rank

#159MediumFrequency: 39.1%

Longest Substring with At Most Two Distinct Characters

Asked at TikTok

Hash Table String Sliding Window

#198

Rank

#2220MediumFrequency: 39.1%

Find All Possible Recipes from Given Supplies

Asked at TikTok

Array Hash Table String Graph Theory Topological Sort Directed Acyclic Graph

#199

Rank

#642HardFrequency: 39.1%

Design Search Autocomplete System

Asked at TikTok

String Depth-First Search Design Trie Sorting Heap (Priority Queue)Data Stream

#200

Rank

#3329MediumFrequency: 39.1%

Find the Length of the Longest Common Prefix

Asked at TikTok

Array Hash Table String Trie

#201

Rank

#1923MediumFrequency: 39.1%

Sentence Similarity III

Asked at TikTok

Array Two Pointers String

#202

Rank

#1567MediumFrequency: 38.9%

Maximum Number of Vowels in a Substring of Given Length

Asked at Amazon

String Sliding Window

#203

Rank

#214HardFrequency: 38.2%

Shortest Palindrome

Asked at Google

String Rolling Hash String Matching Hash Function Manacher Z Algorithm Knuth–Morris–Pratt Algorithm

#204

Rank

#30HardFrequency: 38.2%

Substring with Concatenation of All Words

Asked at Amazon

Hash Table String Sliding Window

#205

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#696EasyFrequency: 38.2%

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Asked at Microsoft

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#206

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#990EasyFrequency: 37.9%

Verifying an Alien Dictionary

Array Hash Table String

#207

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#1756MediumFrequency: 37%

Minimum Deletions to Make String Balanced

Asked at Microsoft

String Dynamic Programming Stack

#208

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#727HardFrequency: 36.9%

Minimum Window Subsequence

Asked at Airbnb

String Dynamic Programming Sliding Window

#209

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#97MediumFrequency: 36.7%

Interleaving String

Asked at Amazon

String Dynamic Programming

#210

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#3931MediumFrequency: 35.9%

Process String with Special Operations I

Asked at Amazon

String Simulation

#211

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#2687HardFrequency: 35.8%

Lexicographically Smallest Beautiful String

Asked at Google

#212

Rank

#2577HardFrequency: 35.7%

Count Palindromic Subsequences

Asked at Microsoft

String Dynamic Programming

#213

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#2520MediumFrequency: 35.6%

Using a Robot to Print the Lexicographically Smallest String

Asked at Salesforce

Hash Table String Stack Greedy

#214

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#664HardFrequency: 35.6%

Strange Printer

Asked at Salesforce

String Dynamic Programming

#215

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#1159MediumFrequency: 35.1%

Smallest Subsequence of Distinct Characters

Asked at Amazon

String Stack Greedy Monotonic Stack

#216

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#2373MediumFrequency: 35.1%

Apply Discount to Prices

Asked at Amazon

#217

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#800MediumFrequency: 35%

Letter Case Permutation

String Backtracking Bit Manipulation

#218

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#468MediumFrequency: 35%

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#219

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#635MediumFrequency: 35%

Design Log Storage System

Hash Table String Design Ordered Set

#220

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#1076MediumFrequency: 35%

Brace Expansion

String Backtracking Stack Breadth-First Search Sorting

#221

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#459EasyFrequency: 34.8%

Repeated Substring Pattern

Asked at Google

String String Matching Z Algorithm Knuth–Morris–Pratt Algorithm

#222

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#874EasyFrequency: 34.8%

Backspace String Compare

Asked at Google

Two Pointers String Stack Simulation

#223

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#722MediumFrequency: 34.3%

Remove Comments

Asked at Microsoft

#224

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#1873EasyFrequency: 34.3%

Longest Nice Substring

Asked at Microsoft

Hash Table String Divide and Conquer Bit Manipulation Sliding Window

#225

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#869HardFrequency: 34.2%

Similar String Groups

Asked at DoorDash

Array Hash Table String Depth-First Search Breadth-First Search Union-Find

#226

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#862MediumFrequency: 33.7%

Find And Replace in String

Asked at Google

Array Hash Table String Sorting

#227

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#1078EasyFrequency: 33.7%

Remove Outermost Parentheses

Asked at Google

String Stack Bracket Sequences

#228

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#3379EasyFrequency: 33.7%

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#229

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#782EasyFrequency: 33.3%

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Asked at Amazon

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#230

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#3410HardFrequency: 33.3%

Find Longest Self-Contained Substring

Asked at Amazon

Hash Table String Sorting

#231

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#1272MediumFrequency: 33.3%

Invalid Transactions

Asked at Oracle

Array Hash Table String Sorting

#232

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#541EasyFrequency: 33.1%

Reverse String II

Asked at Google

Two Pointers String

#233

Rank

#3267MediumFrequency: 33.1%

Find Longest Special Substring That Occurs Thrice I

Asked at Google

Hash Table String Binary Search Sliding Window Counting

#234

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#247MediumFrequency: 33%

Strobogrammatic Number II

Array String Recursion

#235

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#886MediumFrequency: 33%

Score of Parentheses

Asked at TikTok

String Stack Bracket Sequences

#236

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#616MediumFrequency: 33%

Add Bold Tag in String

Asked at TikTok

Array Hash Table String Trie String Matching Aho–Corasick Algorithm

#237

Rank

#1122HardFrequency: 33%

Longest Duplicate Substring

Asked at TikTok

String Binary Search Sliding Window Rolling Hash Suffix Array Hash Function Suffix Automaton Suffix Tree Z Algorithm Boyer–Moore String-Search Algorithm

#238

Rank

#1516MediumFrequency: 32.8%

The k-th Lexicographical String of All Happy Strings of Length n

Asked at Microsoft

String Backtracking

#239

Rank

#3425MediumFrequency: 32.8%

Maximum Number of Potholes That Can Be Fixed

Asked at Microsoft

String Greedy Sorting

#240

Rank

#1460MediumFrequency: 32.8%

Number of Substrings Containing All Three Characters

Asked at Microsoft

Hash Table String Sliding Window

#241

Rank

#3396EasyFrequency: 32.8%

Valid Word

Asked at Microsoft

#242

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#241MediumFrequency: 32.3%

Different Ways to Add Parentheses

Asked at Amazon

Math String Dynamic Programming Recursion Memoization Bracket Sequences

#243

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#974MediumFrequency: 32.3%

Reorder Data in Log Files

Asked at Amazon

Array String Sorting

#244

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#2470MediumFrequency: 32.3%

Removing Stars From a String

Asked at Amazon

String Stack Simulation

#245

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#1205EasyFrequency: 31.9%

Defanging an IP Address

#246

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#1895MediumFrequency: 31.8%

Minimum Number of Operations to Move All Balls to Each Box

Asked at Google

Array String Prefix Sum

#247

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#2360HardFrequency: 31.3%

Substring With Largest Variance

Asked at Amazon

Hash Table String Dynamic Programming Enumeration

#248

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#3018MediumFrequency: 31.3%

Make String a Subsequence Using Cyclic Increments

Asked at Amazon

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#249

Rank

#2021MediumFrequency: 31.3%

Remove All Occurrences of a Substring

Asked at Infosys

String Stack Simulation

#250

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#3983HardFrequency: 31.3%

Minimum Operations to Equalize Binary String

Asked at Infosys

Math String Breadth-First Search Union-Find Ordered Set

#251

Rank

#166MediumFrequency: 31.1%

Fraction to Recurring Decimal

Asked at Google

Hash Table Math String

#252

Rank

#409EasyFrequency: 31.1%

Longest Palindrome

Asked at Google

Hash Table String Greedy

#253

Rank

#1449MediumFrequency: 31.1%

Print Words Vertically

Asked at Microsoft

Array String Simulation

#254

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#1700MediumFrequency: 31.1%

Minimum Time to Make Rope Colorful

Asked at Microsoft

Array String Dynamic Programming Greedy

#255

Rank

#2076EasyFrequency: 31.1%

Sum of Digits of String After Convert

Asked at Microsoft

String Simulation

#256

Rank

#1781EasyFrequency: 30.7%

Check If Two String Arrays are Equivalent

#257

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#271MediumFrequency: 30.4%

Encode and Decode Strings

Asked at Google

Array String Design

#258

Rank

#962MediumFrequency: 30.2%

Flip String to Monotone Increasing

Asked at Amazon

String Dynamic Programming

#259

Rank

#1890MediumFrequency: 30.2%

Sum of Beauty of All Substrings

Asked at Amazon

Hash Table String Counting

#260

Rank

#686MediumFrequency: 29.7%

Repeated String Match

Asked at Google

String String Matching Z Algorithm Knuth–Morris–Pratt Algorithm Boyer–Moore String-Search Algorithm

#261

Rank

#1537EasyFrequency: 29.7%

Maximum Score After Splitting a String

Asked at Google

String Prefix Sum

#262

Rank

#2059MediumFrequency: 29.7%

Unique Length-3 Palindromic Subsequences

Asked at Google

Hash Table String Bit Manipulation Prefix Sum

#263

Rank

#691HardFrequency: 29.5%

Stickers to Spell Word

Array Hash Table String Dynamic Programming Backtracking Bit Manipulation Memoization Bitmask

#264

Rank

#839MediumFrequency: 29.5%

Short Encoding of Words

Array Hash Table String Trie

#265

Rank

#736HardFrequency: 29.5%

Parse Lisp Expression

Hash Table String Stack Recursion

#266

Rank

#1651EasyFrequency: 29.3%

Shuffle String

Asked at Microsoft

#267

Rank

#1770MediumFrequency: 29.3%

Minimum Deletions to Make Character Frequencies Unique

Asked at Microsoft

Hash Table String Greedy Sorting

#268

Rank

#2475MediumFrequency: 29.3%

Largest Palindromic Number

Asked at Microsoft

Hash Table String Greedy Counting

#269

Rank

#2487MediumFrequency: 29.3%

Optimal Partition of String

Asked at Microsoft

Hash Table String Greedy

#270

Rank

#557EasyFrequency: 29.1%

Reverse Words in a String III

Asked at Amazon

Two Pointers String

#271

Rank

#1619EasyFrequency: 29.1%

Path Crossing

Asked at Amazon

Hash Table String

#272

Rank

#1350MediumFrequency: 28.9%

Remove Sub-Folders from the Filesystem

Asked at Google

Array String Depth-First Search Trie

#273

Rank

#520EasyFrequency: 28.1%

Detect Capital

Asked at Google

#274

Rank

#2378MediumFrequency: 28.1%

Sender With Largest Word Count

Asked at Google

Array Hash Table String Counting

#275

Rank

#2389HardFrequency: 28.1%

Design a Text Editor

Asked at Google

Linked List String Stack Design Simulation Doubly-Linked List

#276

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#539MediumFrequency: 28.1%

Minimum Time Difference

Asked at Google

Array Math String Sorting

#277

Rank

#1093HardFrequency: 27.8%

Recover a Tree From Preorder Traversal

Asked at Amazon

String Tree Depth-First Search Binary Tree

#278

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#2456MediumFrequency: 27.8%

Construct Smallest Number From DI String

Asked at Amazon

String Backtracking Stack Greedy

#279

Rank

#1744HardFrequency: 27.8%

Number of Ways to Form a Target String Given a Dictionary

Array String Dynamic Programming

#280

Rank

#2598EasyFrequency: 27.7%

Shortest Distance to Target String in a Circular Array

Asked at Salesforce

#281

Rank

#3445MediumFrequency: 27.7%

Lexicographically Minimum String After Removing Stars

Asked at Salesforce

Hash Table String Stack Greedy Heap (Priority Queue)

#282

Rank

#591HardFrequency: 27.3%

Tag Validator

Asked at Microsoft

#283

Rank

#1012HardFrequency: 27.3%

Equal Rational Numbers

Asked at Microsoft

#284

Rank

#1356HardFrequency: 27.3%

Minimum Number of Moves to Make Palindrome

Asked at Microsoft

Two Pointers String Greedy Binary Indexed Tree

#285

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#1363EasyFrequency: 27.3%

Greatest English Letter in Upper and Lower Case

Asked at Microsoft

Hash Table String Enumeration

#286

Rank

#1473MediumFrequency: 27.3%

Find the Longest Substring Containing Vowels in Even Counts

Asked at Microsoft

Hash Table String Bit Manipulation Prefix Sum

#287

Rank

#1532EasyFrequency: 27.3%

Reformat The String

Asked at Microsoft

#288

Rank

#1678MediumFrequency: 27.3%

Number of Ways to Split a String

Asked at Microsoft

#289

Rank

#1698EasyFrequency: 27.3%

Replace All ?'s to Avoid Consecutive Repeating Characters

Asked at Microsoft

#290

Rank

#1743MediumFrequency: 27.3%

Count Substrings That Differ by One Character

Asked at Microsoft

Hash Table String Dynamic Programming Enumeration

#291

Rank

#2033MediumFrequency: 27.3%

The Number of Full Rounds You Have Played

Asked at Microsoft

#292

Rank

#2082MediumFrequency: 27.3%

Minimum Cost to Separate Sentence Into Rows

Asked at Microsoft

String Dynamic Programming

#293

Rank

#2243EasyFrequency: 27.3%

Check if All A's Appears Before All B's

Asked at Microsoft

#294

Rank

#2471MediumFrequency: 27.3%

Minimum Amount of Time to Collect Garbage

Asked at Microsoft

Array String Prefix Sum

#295

Rank

#2593MediumFrequency: 27.3%

Number of Distinct Binary Strings After Applying Operations

Asked at Microsoft

#296

Rank

#657EasyFrequency: 27.2%

Robot Return to Origin

Asked at Google

String Simulation

#297

Rank

#1818MediumFrequency: 27.2%

Maximum Score From Removing Substrings

Asked at Google

String Stack Greedy

#298

Rank

#1360MediumFrequency: 26.7%

Maximum Length of a Concatenated String with Unique Characters

Array String Backtracking Bit Manipulation

#299

Rank

#1737EasyFrequency: 26.7%

Maximum Nesting Depth of the Parentheses

String Stack Bracket Sequences

#300

Rank

#3707MediumFrequency: 26.7%

Find the Most Common Response

Array Hash Table String Counting

#301

Rank

#837EasyFrequency: 26.5%

Most Common Word

Asked at Amazon

Array Hash Table String Counting

#302

Rank

#1044EasyFrequency: 26.5%

Find Common Characters

Asked at Amazon

Array Hash Table String

#303

Rank

#2032EasyFrequency: 26.5%

Largest Odd Number in String

Asked at Amazon

Math String Greedy

#304

Rank

#2325MediumFrequency: 26.5%

Number of Ways to Select Buildings

Asked at Amazon

String Dynamic Programming Prefix Sum

#305

Rank

#2340HardFrequency: 26.5%

Total Appeal of A String

Asked at Amazon

Hash Table String Dynamic Programming

#306

Rank

#3275EasyFrequency: 26.5%

Minimum Number of Pushes to Type Word I

Asked at Amazon

Math String Greedy

#307

Rank

#3276MediumFrequency: 26.5%

Minimum Number of Pushes to Type Word II

Asked at Amazon

Hash Table String Greedy Sorting Counting

#308

Rank

#3408EasyFrequency: 26.5%

Count the Number of Special Characters I

Asked at Amazon

Hash Table String

#309

Rank

#3684EasyFrequency: 26.5%

Substring Matching Pattern

Asked at Amazon

String String Matching

#310

Rank

#3768EasyFrequency: 26.5%

Check If Digits Are Equal in String After Operations I

Asked at Amazon

Math String Simulation Combinatorics Number Theory

#311

Rank

#474MediumFrequency: 26.3%

Ones and Zeroes

Asked at Google

Array String Dynamic Programming Knapsack Problem 0-1 Knapsack

#312

Rank

#827MediumFrequency: 26.3%

Expressive Words

Asked at Google

Array Two Pointers String

#313

Rank

#1666EasyFrequency: 26.3%

Make The String Great

Asked at Google

#314

Rank

#2427EasyFrequency: 26.3%

First Letter to Appear Twice

Asked at Google

Hash Table String Bit Manipulation Counting

#315

Rank

#388MediumFrequency: 26.3%

Longest Absolute File Path

Asked at Google

String Stack Depth-First Search

#316

Rank

#1483MediumFrequency: 25.4%

Rank Teams by Votes

Asked at Google

Array Hash Table String Sorting Counting

#317

Rank

#2017MediumFrequency: 25.4%

Minimum Number of Flips to Make the Binary String Alternating

Asked at Google

String Dynamic Programming Sliding Window

#318

Rank

#299MediumFrequency: 25.4%

Bulls and Cows

Asked at Google

Hash Table String Counting

#319

Rank

#318MediumFrequency: 25.4%

Maximum Product of Word Lengths

Asked at Google

Array String Bit Manipulation

#320

Rank

#1283EasyFrequency: 25.3%

Reformat Date

Asked at Oracle

#321

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#1160MediumFrequency: 25.3%

Letter Tile Possibilities

Asked at Oracle

Hash Table String Backtracking Counting

#322

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#1437HardFrequency: 25.3%

Minimum Insertion Steps to Make a String Palindrome

Asked at Oracle

String Dynamic Programming

#323

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#2173EasyFrequency: 25.3%

Number of Valid Words in a Sentence

Asked at Oracle

#324

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#433MediumFrequency: 25.1%

Minimum Genetic Mutation

Asked at Amazon

Hash Table String Breadth-First Search Bidirectional Search

#325

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#449MediumFrequency: 25.1%

Serialize and Deserialize BST

Asked at Amazon

String Tree Depth-First Search Breadth-First Search Design Binary Search Tree Binary Tree

#326

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#926MediumFrequency: 25.1%

Find and Replace Pattern

Asked at Amazon

Array Hash Table String

#327

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#935HardFrequency: 25.1%

Orderly Queue

Asked at Amazon

Math String Sorting Lexicographically Minimal String Rotation

#328

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#1381HardFrequency: 25.1%

Maximum Score Words Formed by Letters

Asked at Amazon

Array Hash Table String Dynamic Programming Backtracking Bit Manipulation Counting Bitmask

#329

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#2921HardFrequency: 25.1%

Count Stepping Numbers in Range

Asked at Amazon

String Dynamic Programming

#330

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#4220MediumFrequency: 25.1%

Minimum Operations to Sort a String

Asked at Amazon

#331

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#639HardFrequency: 25.1%

Decode Ways II

String Dynamic Programming

#332

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#1667MediumFrequency: 25.1%

Find Kth Bit in Nth Binary String

String Recursion Simulation

#333

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#3871EasyFrequency: 25.1%

Minimum Deletions for At Most K Distinct Characters

Hash Table String Greedy Sorting Counting

#334

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#1637HardFrequency: 25%

String Compression II

Asked at Microsoft

String Dynamic Programming

#335

Rank

#952MediumFrequency: 25%

Word Subsets

Asked at Microsoft

Array Hash Table String

#336

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#358HardFrequency: 24.6%

Rearrange String k Distance Apart

Asked at TikTok

Hash Table String Greedy Sorting Heap (Priority Queue)Counting

#337

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#965EasyFrequency: 24.4%

Unique Email Addresses

Asked at Google

Array Hash Table String

#338

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#1934MediumFrequency: 24.4%

Evaluate the Bracket Pairs of a String

Asked at Google

Array Hash Table String

#339

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#2292EasyFrequency: 24.4%

Counting Words With a Given Prefix

Asked at Google

Array String String Matching

#340

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#2550MediumFrequency: 24.4%

Words Within Two Edits of Dictionary

Asked at Google

Array String Trie

#341

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#504EasyFrequency: 23.6%

Base 7

Asked at Amazon

#342

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#640MediumFrequency: 23.6%

Solve the Equation

Asked at Amazon

Math String Simulation Linear Algebra

#343

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#1060MediumFrequency: 23.6%

Longest Repeating Substring

Asked at Amazon

String Binary Search Dynamic Programming Rolling Hash Suffix Array Hash Function Suffix Automaton Suffix Tree

#344

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#1454EasyFrequency: 23.6%

Remove Palindromic Subsequences

Asked at Amazon

Two Pointers String

#345

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#1850MediumFrequency: 23.6%

Minimum Length of String After Deleting Similar Ends

Asked at Amazon

Two Pointers String

#346

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#1997HardFrequency: 23.6%

Next Palindrome Using Same Digits

Asked at Amazon

Two Pointers String

#347

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#2244MediumFrequency: 23.6%

Number of Laser Beams in a Bank

Asked at Amazon

Array Math String Matrix

#348

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#2309MediumFrequency: 23.6%

Maximize Number of Subsequences in a String

Asked at Amazon

String Greedy Prefix Sum

#349

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#2348MediumFrequency: 23.6%

Count Number of Texts

Asked at Amazon

Hash Table Math String Dynamic Programming

#350

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#2429MediumFrequency: 23.6%

Design a Food Rating System

Asked at Amazon

Array Hash Table String Design Heap (Priority Queue)Ordered Set

#351

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#2884HardFrequency: 23.6%

Length of the Longest Valid Substring

Asked at Amazon

Array Hash Table String Sliding Window

#352

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#3210MediumFrequency: 23.6%

Count Beautiful Substrings I

Asked at Amazon

Hash Table Math String Enumeration Number Theory Prefix Sum

#353

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#3453MediumFrequency: 23.6%

Generate Binary Strings Without Adjacent Zeros

Asked at Amazon

String Backtracking Bit Manipulation

#354

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#3692HardFrequency: 23.6%

Shortest Matching Substring

Asked at Amazon

Two Pointers String Binary Search String Matching

#355

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#405EasyFrequency: 23.4%

Convert a Number to Hexadecimal

Math String Bit Manipulation

#356

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#746HardFrequency: 23.4%

Prefix and Suffix Search

Array Hash Table String Design Trie

#357

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#1899EasyFrequency: 23.4%

Count Items Matching a Rule

#358

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#1960EasyFrequency: 23.4%

Check if the Sentence Is Pangram

Hash Table String

#359

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#754HardFrequency: 23.3%

Cracking the Safe

Asked at Google

String Depth-First Search Graph Theory Eulerian Circuit Eulerian Path Eulerian Graph

#360

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#868MediumFrequency: 23.3%

Push Dominoes

Asked at Google

Two Pointers String Dynamic Programming

#361

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#981EasyFrequency: 23.3%

Delete Columns to Make Sorted

Asked at Google

Array String Longest Increasing Subsequence

#362

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#1557MediumFrequency: 23.3%

Check If a String Contains All Binary Codes of Size K

Asked at Google

Hash Table String Bit Manipulation Rolling Hash Hash Function Directed Acyclic Graph

#363

Rank

#1030MediumFrequency: 23.3%

Smallest String Starting From Leaf

Asked at Google

String Backtracking Tree Depth-First Search Binary Tree

#364

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#3447EasyFrequency: 23.3%

Clear Digits

Asked at Google

String Stack Simulation

#365

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#3603HardFrequency: 23.3%

Check if DFS Strings Are Palindromes

Asked at Google

Array Hash Table String Tree Depth-First Search Hash Function

#366

Rank

#3195MediumFrequency: 22.5%

Separate Black and White Balls

Asked at Microsoft

Two Pointers String Greedy

#367

Rank

#878MediumFrequency: 22.5%

Shifting Letters

Asked at Microsoft

Array String Prefix Sum

#368

Rank

#1006MediumFrequency: 22.5%

Vowel Spellchecker

Asked at Microsoft

Array Hash Table String

#369

Rank

#524MediumFrequency: 22.1%

Longest Word in Dictionary through Deleting

Asked at Google

Array Two Pointers String Sorting

#370

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#551EasyFrequency: 22.1%

Student Attendance Record I

Asked at Google

#371

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#676MediumFrequency: 22.1%

Implement Magic Dictionary

Asked at Google

Hash Table String Depth-First Search Design Trie

#372

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#992MediumFrequency: 22.1%

Delete Columns to Make Sorted II

Asked at Google

Array String Greedy

#373

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#1097HardFrequency: 22.1%

Stream of Characters

Asked at Google

Array String Design Trie Data Stream Aho–Corasick Algorithm

#374

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#1443HardFrequency: 22.1%

Minimum Distance to Type a Word Using Two Fingers

Asked at Google

String Dynamic Programming

#375

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#1632MediumFrequency: 22.1%

Number of Good Ways to Split a String

Asked at Google

Hash Table String Dynamic Programming Bit Manipulation Prefix Sum

#376

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#1715MediumFrequency: 22.1%

Split a String Into the Max Number of Unique Substrings

Asked at Google

Hash Table String Backtracking

#377

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#2001MediumFrequency: 22.1%

Jump Game VII

Asked at Google

String Dynamic Programming Sliding Window Prefix Sum

#378

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#2137EasyFrequency: 22.1%

Final Value of Variable After Performing Operations

Asked at Google

Array String Simulation

#379

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#3786MediumFrequency: 22.1%

Longest Palindromic Subsequence After at Most K Operations

Asked at Google

String Dynamic Programming

#380

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#1777MediumFrequency: 22%

Determine if Two Strings Are Close

Hash Table String Sorting Counting

#381

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#3451MediumFrequency: 22%

String Compression III

#382

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#2881EasyFrequency: 22%

Split Strings by Separator

#383

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#737MediumFrequency: 22%

Sentence Similarity II

Array Hash Table String Depth-First Search Breadth-First Search Union-Find

#384

Rank

#1508HardFrequency: 22%

Longest Happy Prefix

String Rolling Hash String Matching Hash Function Z Algorithm Knuth–Morris–Pratt Algorithm

#385

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#87HardFrequency: 21.9%

Scramble String

Asked at Amazon

String Dynamic Programming

#386

Rank

#606MediumFrequency: 21.9%

Construct String from Binary Tree

Asked at Amazon

String Tree Depth-First Search Binary Tree

#387

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#872MediumFrequency: 21.9%

Split Array into Fibonacci Sequence

Asked at Amazon

String Backtracking

#388

Rank

#1197HardFrequency: 21.9%

Parsing A Boolean Expression

Asked at Amazon

String Stack Recursion

#389

Rank

#1520MediumFrequency: 21.9%

Number of Steps to Reduce a Number in Binary Representation to One

Asked at Amazon

String Bit Manipulation Simulation

#390

Rank

#1524EasyFrequency: 21.9%

String Matching in an Array

Asked at Amazon

Array String String Matching

#391

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#1644HardFrequency: 21.9%

Maximum Number of Non-Overlapping Substrings

Asked at Amazon

Hash Table String Greedy Sorting

#392

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#2197MediumFrequency: 21.9%

Decode the Slanted Ciphertext

Asked at Amazon

String Simulation

#393

Rank

#2232MediumFrequency: 21.9%

Adding Spaces to a String

Asked at Amazon

Array Two Pointers String Simulation

#394

Rank

#2405MediumFrequency: 21.9%

Minimum Number of Keypresses

Asked at Amazon

Hash Table String Greedy Sorting Counting

#395

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#2555MediumFrequency: 21.9%

Design SQL

Asked at Amazon

Array Hash Table String Design

#396

Rank

#2572MediumFrequency: 21.9%

Append Characters to String to Make Subsequence

Asked at Amazon

Two Pointers String Greedy

#397

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#2669MediumFrequency: 21.9%

Find the Substring With Maximum Cost

Asked at Amazon

Array Hash Table String Dynamic Programming

#398

Rank

#2713MediumFrequency: 21.9%

Find the Divisibility Array of a String

Asked at Amazon

Array Math String

#399

Rank

#3354MediumFrequency: 21.9%

Replace Question Marks in String to Minimize Its Value

Asked at Amazon

Hash Table String Greedy Sorting Heap (Priority Queue)Counting

#400

Rank

#3479MediumFrequency: 21.9%

Count the Number of Substrings With Dominant Ones

Asked at Amazon

String Enumeration

#401

Rank

#4131MediumFrequency: 21.9%

Minimum Flips to Make Binary String Coherent

Asked at Amazon

#402

Rank

#929MediumFrequency: 21.5%

Groups of Special-Equivalent Strings

Array Hash Table String Sorting

#403

Rank

#1271MediumFrequency: 21.5%

Web Crawler

String Depth-First Search Breadth-First Search Interactive

#404

Rank

#2140HardFrequency: 21.5%

Longest Subsequence Repeated k Times

Hash Table Two Pointers String Backtracking Counting Enumeration

#405

Rank

#2465MediumFrequency: 21.5%

Shifting Letters II

Array String Prefix Sum

#406

Rank

#331MediumFrequency: 20.9%

Verify Preorder Serialization of a Binary Tree

Asked at Google

String Stack Tree Binary Tree

#407

Rank

#418MediumFrequency: 20.9%

Sentence Screen Fitting

Asked at Google

Array String Dynamic Programming

#408

Rank

#481MediumFrequency: 20.9%

Magical String

Asked at Google

Two Pointers String

#409

Rank

#514HardFrequency: 20.9%

Freedom Trail

Asked at Google

String Dynamic Programming Depth-First Search Breadth-First Search

#410

Rank

#979EasyFrequency: 20.9%

DI String Match

Asked at Google

Array Two Pointers String Greedy

#411

Rank

#1858EasyFrequency: 20.9%

Latest Time by Replacing Hidden Digits

Asked at Google

#412

Rank

#1986HardFrequency: 20.9%

Largest Color Value in a Directed Graph

Asked at Google

Hash Table String Dynamic Programming Graph Theory Topological Sort Memoization Counting Directed Acyclic Graph

#413

Rank

#2219EasyFrequency: 20.9%

Maximum Number of Words Found in Sentences

Asked at Google

#414

Rank

#482EasyFrequency: 20.9%

License Key Formatting

Asked at Google

#415

Rank

#681MediumFrequency: 20.9%

Next Closest Time

Asked at Google

Hash Table String Backtracking Enumeration

#416

Rank

#3905MediumFrequency: 20.9%

Partition String

Asked at Google

Hash Table String Trie Simulation

#417

Rank

#3305HardFrequency: 20.3%

Count Prefix and Suffix Pairs II

Array String Trie Rolling Hash String Matching Hash Function Z Algorithm

#418

Rank

#1838MediumFrequency: 20.3%

Number of Distinct Substrings in a String

String Trie Rolling Hash Suffix Array Hash Function

#419

Rank

#3754MediumFrequency: 20.3%

Maximum Manhattan Distance After K Changes

Hash Table Math String Counting

#420

Rank

#2044MediumFrequency: 20.3%

Number of Wonderful Substrings

Hash Table String Bit Manipulation Prefix Sum

#421

Rank

#537MediumFrequency: 20%

Complex Number Multiplication

Asked at Amazon

Math String Simulation

#422

Rank

#1075EasyFrequency: 20%

Index Pairs of a String

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Array String Trie Sorting Aho–Corasick Algorithm

#423

Rank

#1084MediumFrequency: 20%

Find K-Length Substrings With No Repeated Characters

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Hash Table String Sliding Window

#424

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#1089EasyFrequency: 20%

Remove Vowels from a String

Asked at Amazon

#425

Rank

#1736HardFrequency: 20%

Build Binary Expression Tree From Infix Expression

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String Stack Tree Binary Tree

#426

Rank

#1919MediumFrequency: 20%

Sort Features by Popularity

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Array Hash Table String Sorting

#427

Rank

#2163EasyFrequency: 20%

Kth Distinct String in an Array

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Array Hash Table String Counting

#428

Rank

#2326HardFrequency: 20%

Sum of Scores of Built Strings

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String Binary Search Rolling Hash Suffix Array String Matching Hash Function Z Algorithm Knuth–Morris–Pratt Algorithm

#429

Rank

#2372EasyFrequency: 20%

Rearrange Characters to Make Target String

Asked at Amazon

Hash Table String Counting

#430

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#2468MediumFrequency: 20%

Valid Palindrome IV

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Two Pointers String

#431

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#3207EasyFrequency: 20%

Make Three Strings Equal

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#432

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#3208HardFrequency: 20%

Count Beautiful Substrings II

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Hash Table Math String Number Theory Prefix Sum

#433

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#3405MediumFrequency: 20%

Count the Number of Special Characters II

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Hash Table String

#434

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#4130MediumFrequency: 20%

Maximum Score After Binary Swaps

Asked at Amazon

Array String Greedy Heap (Priority Queue)

#435

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#4177EasyFrequency: 20%

Reverse String Prefix

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Two Pointers String

#436

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#4192HardFrequency: 20%

Minimum Cost to Partition a Binary String

Asked at Amazon

String Divide and Conquer Prefix Sum

#437

Rank

#4142MediumFrequency: 20%

Maximum Total Value of Covered Indices

Asked at Amazon

Array String Dynamic Programming Greedy

#438

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#961EasyFrequency: 20%

Long Pressed Name

Asked at LinkedIn

Two Pointers String

#439

Rank

#544MediumFrequency: 19.5%

Output Contest Matches

Asked at Google

String Recursion Simulation

#440

Rank

#604EasyFrequency: 19.5%

Design Compressed String Iterator

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Array String Design Iterator

#441

Rank

#734EasyFrequency: 19.5%

Sentence Similarity

Asked at Google

Array Hash Table String

#442

Rank

#884HardFrequency: 19.5%

K-Similar Strings

Asked at Google

Hash Table String Breadth-First Search

#443

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#1000HardFrequency: 19.5%

Delete Columns to Make Sorted III

Asked at Google

Array String Dynamic Programming

#444

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#1065MediumFrequency: 19.5%

Binary String With Substrings Representing 1 To N

Asked at Google

Hash Table String Bit Manipulation Sliding Window

#445

Rank

#1123EasyFrequency: 19.5%

Single-Row Keyboard

Asked at Google

Hash Table String

#446

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#1238MediumFrequency: 19.5%

Alphabet Board Path

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Hash Table String

#447

Rank

#2115HardFrequency: 19.5%

Number of Unique Good Subsequences

Asked at Google

String Dynamic Programming

#448

Rank

#2377EasyFrequency: 19.5%

Check if Number Has Equal Digit Count and Digit Value

Asked at Google

Hash Table String Counting

#449

Rank

#2395MediumFrequency: 19.5%

Longest Binary Subsequence Less Than or Equal to K

Asked at Google

String Dynamic Programming Greedy Memoization

#450

Rank

#2494HardFrequency: 19.5%

Sum of Prefix Scores of Strings

Asked at Google

Array String Trie Counting

#451

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#2536EasyFrequency: 19.5%

Determine if Two Events Have Conflict

Asked at Google

#452

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#3024HardFrequency: 19.5%

String Transformation

Asked at Google

Math String Dynamic Programming String Matching

#453

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#3057HardFrequency: 19.5%

Count K-Subsequences of a String With Maximum Beauty

Asked at Google

Hash Table Math String Greedy Sorting Combinatorics Fermat's Little Theorem

#454

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#3376HardFrequency: 19.5%

Longest Common Suffix Queries

Asked at Google

Array String Trie

#455

Rank

#522MediumFrequency: 19.5%

Longest Uncommon Subsequence II

Asked at Google

Array Hash Table Two Pointers String Sorting

#456

Rank

#953EasyFrequency: 19.5%

Reverse Only Letters

Asked at Google

Two Pointers String

#457

Rank

#3303HardFrequency: 19.5%

Find Beautiful Indices in the Given Array II

Asked at Google

Two Pointers String Binary Search Rolling Hash String Matching Hash Function Z Algorithm Knuth–Morris–Pratt Algorithm Boyer–Moore String-Search Algorithm

#458

Rank

#3821MediumFrequency: 19.5%

Count Cells in Overlapping Horizontal and Vertical Substrings

Asked at Google

Array String Rolling Hash String Matching Matrix Hash Function

#459

Rank

#829MediumFrequency: 19.5%

Subdomain Visit Count

Asked at Google

Array Hash Table String Counting

#460

Rank

#4183MediumFrequency: 19.5%

Count Caesar Cipher Pairs

Asked at Google

Array Hash Table Math String Counting

#461

Rank

#2300MediumFrequency: 19.5%

Construct String With Repeat Limit

Asked at Microsoft

Hash Table String Greedy Heap (Priority Queue)Counting

#462

Rank

#2107MediumFrequency: 19.5%

Find Unique Binary String

Asked at Microsoft

Array Hash Table String Backtracking

#463

Rank

#3753EasyFrequency: 19.5%

Maximum Difference Between Even and Odd Frequency I

Asked at Microsoft

Hash Table String Counting

#464

Rank

#3761HardFrequency: 19.5%

Maximum Difference Between Even and Odd Frequency II

Asked at Microsoft

String Sliding Window Enumeration Prefix Sum

#465

Rank

#527HardFrequency: 18%

Word Abbreviation

Asked at Google

Array String Greedy Trie Sorting

#466

Rank

#749EasyFrequency: 18%

Shortest Completing Word

Asked at Google

Array Hash Table String

#467

Rank

#857EasyFrequency: 18%

Positions of Large Groups

Asked at Google

#468

Rank

#942HardFrequency: 18%

Super Palindromes

Asked at Google

Math String Enumeration

#469

Rank

#1188HardFrequency: 18%

Brace Expansion II

Asked at Google

Hash Table String Backtracking Stack Breadth-First Search Sorting

#470

Rank

#1244HardFrequency: 18%

Distinct Echo Substrings

Asked at Google

String Trie Rolling Hash Suffix Array Hash Function Suffix Automaton Suffix Tree

#471

Rank

#1251HardFrequency: 18%

Longest Chunked Palindrome Decomposition

Asked at Google

Two Pointers String Dynamic Programming Greedy Rolling Hash Hash Function

#472

Rank

#1543MediumFrequency: 18%

Simplified Fractions

Asked at Google

Math String Number Theory Euclidean Algorithm Greatest Common Divisor

#473

Rank

#1714EasyFrequency: 18%

Rearrange Spaces Between Words

Asked at Google

#474

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#2286HardFrequency: 18%

Minimum Time to Remove All Cars Containing Illegal Goods

Asked at Google

String Dynamic Programming

#475

Rank

#2341EasyFrequency: 18%

Count Prefixes of a Given String

Asked at Google

#476

Rank

#2401EasyFrequency: 18%

Count Asterisks

Asked at Google

#477

Rank

#2569HardFrequency: 18%

Number of Beautiful Partitions

Asked at Google

String Dynamic Programming Prefix Sum

#478

Rank

#2615MediumFrequency: 18%

Make Number of Distinct Characters Equal

Asked at Google

Hash Table String Counting

#479

Rank

#3266MediumFrequency: 18%

Find Longest Special Substring That Occurs Thrice II

Asked at Google

Hash Table String Binary Search Sliding Window Counting

#480

Rank

#3384MediumFrequency: 18%

Minimum Number of Operations to Make Word K-Periodic

Asked at Google

Hash Table String Counting

#481

Rank

#2528EasyFrequency: 18%

Number of Valid Clock Times

Asked at Google

String Enumeration

#482

Rank

#1739MediumFrequency: 18%

Split Two Strings to Make Palindrome

Asked at Google

Two Pointers String

#483

Rank

#3194EasyFrequency: 18%

Find Words Containing Character

Asked at Google

#484

Rank

#3618HardFrequency: 18%

Find the Original Typed String II

Asked at Google

String Dynamic Programming Prefix Sum

#485

Rank

#1747MediumFrequency: 18%

Lexicographically Smallest String After Applying Operations

Asked at Amazon

String Depth-First Search Breadth-First Search Enumeration

#486

Rank

#3629MediumFrequency: 18%

Total Characters in String After Transformations I

Asked at Amazon

Hash Table Math String Dynamic Programming Counting

#487

Rank

#1058MediumFrequency: 18%

Lexicographically Smallest Equivalent String

Asked at Amazon

String Union-Find

#488

Rank

#4020MediumFrequency: 18%

Lexicographically Smallest Permutation Greater Than Target

Asked at Amazon

Hash Table String Greedy Counting Enumeration

#489

Rank

#4055MediumFrequency: 18%

Longest Balanced Substring I

Asked at Amazon

Hash Table String Counting Enumeration

#490

Rank

#3805MediumFrequency: 18%

Maximize Active Section with Trade I

Asked at Amazon

String Enumeration

#491

Rank

#609MediumFrequency: 17%

Find Duplicate File in System

Array Hash Table String

#492

Rank

#1542EasyFrequency: 17%

Consecutive Characters

#493

Rank

#3174MediumFrequency: 17%

Minimum Number of Changes to Make Binary String Beautiful

#494

Rank

#2221MediumFrequency: 17%

Check if a Parentheses String Can Be Valid

String Stack Greedy Bracket Sequences

#495

Rank

#3349EasyFrequency: 17%

Maximum Length Substring With Two Occurrences

Hash Table String Sliding Window

#496

Rank

#288MediumFrequency: 16.4%

Unique Word Abbreviation

Asked at Google

Array Hash Table String Design

#497

Rank

#293EasyFrequency: 16.4%

Flip Game

Asked at Google

#498

Rank

#320MediumFrequency: 16.4%

Generalized Abbreviation

Asked at Google

String Backtracking Bit Manipulation

#499

Rank

#411HardFrequency: 16.4%

Minimum Unique Word Abbreviation

Asked at Google

Array String Backtracking Bit Manipulation

#500

Rank

#425HardFrequency: 16.4%

Word Squares

Asked at Google

Array String Backtracking Trie

#501

Rank

#471HardFrequency: 16.4%

Encode String with Shortest Length

Asked at Google

String Dynamic Programming

#502

Rank

#484MediumFrequency: 16.4%

Find Permutation

Asked at Google

Array String Stack Greedy

#503

Rank

#521EasyFrequency: 16.4%

Longest Uncommon Subsequence I

Asked at Google

#504

Rank

#760MediumFrequency: 16.4%

Bold Words in String

Asked at Google

Array Hash Table String Trie String Matching Aho–Corasick Algorithm

#505

Rank

#818EasyFrequency: 16.4%

Similar RGB Color

Asked at Google

Math String Enumeration

#506

Rank

#834MediumFrequency: 16.4%

Ambiguous Coordinates

Asked at Google

String Backtracking Enumeration

#507

Rank

#1051MediumFrequency: 16.4%

Shortest Way to Form String

Asked at Google

Two Pointers String Binary Search Greedy

#508

Rank

#1080MediumFrequency: 16.4%

Camelcase Matching

Asked at Google

Array Two Pointers String Trie String Matching

#509

Rank

#1124HardFrequency: 16.4%

String Transforms Into Another String

Asked at Google

Hash Table String Graph Theory

#510

Rank

#1156EasyFrequency: 16.4%

Occurrences After Bigram

Asked at Google

#511

Rank

#1211MediumFrequency: 16.4%

Iterator for Combination

Asked at Google

String Backtracking Design Iterator

#512

Rank

#1273MediumFrequency: 16.4%

Compare Strings by Frequency of the Smallest Character

Asked at Google

Array Hash Table String Binary Search Sorting

#513

Rank

#1384MediumFrequency: 16.4%

Maximum Font to Fit a Sentence in a Screen

Asked at Google

Array String Binary Search Interactive

#514

Rank

#1562MediumFrequency: 16.4%

People Whose List of Favorite Companies Is Not a Subset of Another List

Asked at Google

Array Hash Table String

#515

Rank

#1636MediumFrequency: 16.4%

Number of Substrings With Only 1s

Asked at Google

#516

Rank

#1687HardFrequency: 16.4%

The Most Similar Path in a Graph

Asked at Google

Array String Dynamic Programming Graph Theory

#517

Rank

#1707HardFrequency: 16.4%

Check If String Is Transformable With Substring Sort Operations

Asked at Google

String Greedy Sorting

#518

Rank

#1859MediumFrequency: 16.4%

Change Minimum Characters to Satisfy One of Three Conditions

Asked at Google

Hash Table String Counting Prefix Sum

#519

Rank

#1943MediumFrequency: 16.4%

Count Pairs of Equal Substrings With Minimum Difference

Asked at Google

Hash Table String Greedy

#520

Rank

#1978MediumFrequency: 16.4%

Minimum Adjacent Swaps to Reach the Kth Smallest Number

Asked at Google

Two Pointers String Greedy

#521

Rank

#2008HardFrequency: 16.4%

Minimum Cost to Change the Final Value of Expression

Asked at Google

Math String Dynamic Programming Stack

#522

Rank

#2009MediumFrequency: 16.4%

Longest Word With All Prefixes

Asked at Google

Array String Depth-First Search Trie

#523

Rank

#2256MediumFrequency: 16.4%

Count Words Obtained After Adding a Letter

Asked at Google

Array Hash Table String Bit Manipulation Sorting

#524

Rank

#2311HardFrequency: 16.4%

Minimum White Tiles After Covering With Carpets

Asked at Google

String Dynamic Programming Prefix Sum

#525

Rank

#2345EasyFrequency: 16.4%

Minimum Number of Operations to Convert Time

Asked at Google

#526

Rank

#3361EasyFrequency: 16.4%

Latest Time You Can Obtain After Replacing Characters

Asked at Google

String Enumeration

#527

Rank

#2226EasyFrequency: 16.4%

Rings and Rods

Asked at Google

Hash Table String

#528

Rank

#2346EasyFrequency: 16.4%

Largest 3-Same-Digit Number in String

Asked at Google

#529

Rank

#500EasyFrequency: 16.4%

Keyboard Row

Asked at Google

Array Hash Table String

#530

Rank

#980HardFrequency: 16.4%

Find the Shortest Superstring

Asked at Google

Array String Dynamic Programming Bit Manipulation Bitmask Hamiltonian Path

#531

Rank

#1954EasyFrequency: 16.4%

Replace All Digits with Characters

Asked at Google

#532

Rank

#306MediumFrequency: 16.4%

Additive Number

Asked at Google

String Backtracking

#533

Rank

#4136MediumFrequency: 16.4%

Concatenate Non-Zero Digits and Multiply by Sum II

Asked at Google

Math String Prefix Sum

#534

Rank

#3683MediumFrequency: 16.1%

Find the Lexicographically Largest String From the Box I

Asked at Microsoft

Two Pointers String Enumeration

#535

Rank

#1970EasyFrequency: 16.1%

Sorting the Sentence

Asked at Microsoft

String Sorting Bubble Sort

#536

Rank

#841EasyFrequency: 16.1%

Shortest Distance to a Character

Asked at Microsoft

Array Two Pointers String

#537

Rank

#1133HardFrequency: 16.1%

Last Substring in Lexicographical Order

Asked at Microsoft

Two Pointers String Lyndon Factorization

#538

Rank

#1297EasyFrequency: 16.1%

Maximum Number of Balloons

Asked at Microsoft

Hash Table String Counting

#539

Rank

#649MediumFrequency: 15.7%

Dota2 Senate

Asked at Amazon

String Greedy Queue

#540

Rank

#1353EasyFrequency: 15.7%

Find Resultant Array After Removing Anagrams

Asked at Amazon

Array Hash Table String Sorting

#541

Rank

#2576MediumFrequency: 15.7%

Minimum Penalty for a Shop

Asked at Amazon

String Prefix Sum

#542

Rank

#3939HardFrequency: 15.7%

Process String with Special Operations II

Asked at Amazon

String Simulation

#543

Rank

#2755MediumFrequency: 14.6%

Extra Characters in a String

Asked at Google

Array Hash Table String Dynamic Programming Trie

#544

Rank

#1032MediumFrequency: 14.6%

Satisfiability of Equality Equations

Asked at Google

Array String Union-Find Graph Theory

#545

Rank

#3493MediumFrequency: 14.6%

Maximum Number of Operations to Move Ones to the End

Asked at Google

String Greedy Counting

#546

Rank

#1786EasyFrequency: 14.6%

Count the Number of Consistent Strings

Asked at Google

Array Hash Table String Bit Manipulation Counting

#547

Rank

#1302EasyFrequency: 14.6%

Delete Characters to Make Fancy String

Asked at Google

#548

Rank

#1260EasyFrequency: 14.6%

Day of the Year

Asked at Google

#549

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#2463EasyFrequency: 14.6%

Minimum Recolors to Get K Consecutive Black Blocks

Asked at Google

String Sliding Window

#550

Rank

#3243HardFrequency: 14.6%

Count the Number of Powerful Integers

Asked at Google

Math String Dynamic Programming

#551

Rank

#3637HardFrequency: 14.6%

Count Number of Balanced Permutations

Asked at Google

Math String Dynamic Programming Combinatorics

#552

Rank

#3812MediumFrequency: 14.6%

Smallest Palindromic Rearrangement I

Asked at Google

String Sorting Counting Sort

#553

Rank

#3584MediumFrequency: 14.6%

Find the Lexicographically Smallest Valid Sequence

Asked at Google

Two Pointers String Dynamic Programming Greedy

#554

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#742EasyFrequency: 14.4%

To Lower Case

#555

Rank

#3872EasyFrequency: 14.4%

Find Most Frequent Vowel and Consonant

Hash Table String Counting

#556

Rank

#1807MediumFrequency: 13.2%

Partitioning Into Minimum Number Of Deci-Binary Numbers

Asked at Amazon

#557

Rank

#2128EasyFrequency: 13.2%

Reverse Prefix of Word

Asked at Amazon

Two Pointers String Stack

#558

Rank

#599EasyFrequency: 13.2%

Minimum Index Sum of Two Lists

Asked at Amazon

Array Hash Table String

#559

Rank

#2599MediumFrequency: 13.2%

Take K of Each Character From Left and Right

Asked at Amazon

Hash Table String Sliding Window

#560

Rank

#3617EasyFrequency: 13.2%

Find the Original Typed String I

Asked at Amazon

#561

Rank

#4056MediumFrequency: 13.2%

Longest Balanced Substring II

Asked at Amazon

Hash Table String Prefix Sum

#562

Rank

#592MediumFrequency: 12.6%

Fraction Addition and Subtraction

Asked at Google

Math String Simulation Euclidean Algorithm Greatest Common Divisor

#563

Rank

#3635HardFrequency: 12.6%

Smallest Divisible Digit Product II

Asked at Google

Math String Backtracking Greedy Number Theory

#564

Rank

#420HardFrequency: 12%

Strong Password Checker

Asked at Microsoft

String Greedy Heap (Priority Queue)

#565

Rank

#2887MediumFrequency: 12%

Sort Vowels in a String

Asked at Microsoft

#566

Rank

#1264EasyFrequency: 12%

Maximum Number of Words You Can Type

Asked at Microsoft

Hash Table String

#567

Rank

#1987EasyFrequency: 12%

Substrings of Size Three with Distinct Characters

Asked at Microsoft

Hash Table String Sliding Window Counting

#568

Rank

#1321MediumFrequency: 12%

Get Equal Substrings Within Budget

Asked at Microsoft

String Binary Search Sliding Window Prefix Sum

#569

Rank

#2319HardFrequency: 12%

Longest Substring of One Repeating Character

Asked at Microsoft

Array String Segment Tree Ordered Set

#570

Rank

#1648MediumFrequency: 11.4%

Minimum Insertions to Balance a Parentheses String

String Stack Greedy Bracket Sequences

#571

Rank

#1720EasyFrequency: 11.4%

Crawler Log Folder

Array String Stack

#572

Rank

#2184HardFrequency: 11.4%

Check if an Original String Exists Given Two Encoded Strings

String Dynamic Programming

#573

Rank

#2134MediumFrequency: 10.5%

Maximize the Confusion of an Exam

Asked at Google

String Binary Search Sliding Window Prefix Sum

#574

Rank

#2532EasyFrequency: 10.5%

Remove Letter To Equalize Frequency

Asked at Google

Hash Table String Counting

#575

Rank

#1369MediumFrequency: 10.5%

Minimum Swaps to Make Strings Equal

Asked at Google

Math String Greedy

#576

Rank

#920EasyFrequency: 10.5%

Uncommon Words from Two Sentences

Asked at Google

Hash Table String Counting

#577

Rank

#2800EasyFrequency: 10.5%

Minimum String Length After Removing Substrings

Asked at Google

String Stack Simulation

#578

Rank

#423MediumFrequency: 10.5%

Reconstruct Original Digits from English

Asked at Google

Hash Table Math String

#579

Rank

#3580HardFrequency: 10.5%

Find the Occurrence of First Almost Equal Substring

Asked at Google

String String Matching Knuth–Morris–Pratt Algorithm

#580

Rank

#712MediumFrequency: 10.5%

Minimum ASCII Delete Sum for Two Strings

Asked at Google

String Dynamic Programming Longest Common Subsequence

#581

Rank

#3804HardFrequency: 10.5%

Maximize Active Section with Trade II

Asked at Google

Array String Binary Search Segment Tree

#582

Rank

#3813HardFrequency: 10.5%

Smallest Palindromic Rearrangement II

Asked at Google

Hash Table Math String Combinatorics Counting

#583

Rank

#1512MediumFrequency: 10.3%

Design Underground System

Asked at Amazon

Hash Table String Design

#584

Rank

#1547EasyFrequency: 10.3%

Destination City

Asked at Amazon

Array Hash Table String

#585

Rank

#3235MediumFrequency: 10.3%

Minimum Cost to Convert String I

Asked at Amazon

Array String Graph Theory Shortest Path

#586

Rank

#434EasyFrequency: 10.3%

Number of Segments in a String

Asked at Amazon

#587

Rank

#977HardFrequency: 10.3%

Distinct Subsequences II

Asked at Amazon

String Dynamic Programming

#588

Rank

#1910EasyFrequency: 10.3%

Check if Binary String Has at Most One Segment of Ones

Asked at Amazon

#589

Rank

#1274EasyFrequency: 8.1%

Number of Days Between Two Dates

Asked at Google

#590

Rank

#2079HardFrequency: 8.1%

Delete Duplicate Folders in System

Asked at Google

Array Hash Table String Depth-First Search Trie Sorting Hash Function

#591

Rank

#781HardFrequency: 8.1%

Basic Calculator IV

Asked at Google

Hash Table Math String Stack Recursion

#592

Rank

#1470MediumFrequency: 8.1%

Tweet Counts Per Frequency

Asked at Google

Hash Table String Binary Search Design Sorting Ordered Set

#593

Rank

#3630HardFrequency: 8.1%

Total Characters in String After Transformations II

Asked at Google

Hash Table Math String Dynamic Programming Counting

#594

Rank

#1764EasyFrequency: 8.1%

Maximum Repeating Substring

Asked at Google

String Dynamic Programming String Matching

#595

Rank

#2708HardFrequency: 8.1%

Find the String with LCP

Asked at Google

Array String Dynamic Programming Greedy Union-Find Matrix

#596

Rank

#1026MediumFrequency: 8.1%

String Without AAA or BBB

Asked at Google

#597

Rank

#1208MediumFrequency: 8.1%

Maximum Nesting Depth of Two Valid Parentheses Strings

Asked at Google

String Stack Bracket Sequences

#598

Rank

#2406EasyFrequency: 8.1%

Decode the Message

Asked at Google

Hash Table String

#599

Rank

#3797MediumFrequency: 8.1%

Design Spreadsheet

Asked at Google

Array Hash Table String Design Matrix

#600

Rank

#3860MediumFrequency: 8%

Resulting String After Adjacent Removals

String Stack Simulation

#601

Rank

#916MediumFrequency: 8%

Decoded String at Index

#602

Rank

#1884EasyFrequency: 8%

Minimum Changes To Make Alternating Binary String

#603

Rank

#3019EasyFrequency: 8%

Furthest Point From Origin

String Counting

#604

Rank

#986MediumFrequency: 7.3%

Largest Time for Given Digits

Asked at Microsoft

Array String Backtracking Enumeration

#605

Rank

#2736MediumFrequency: 7.3%

Minimum Additions to Make Valid String

Asked at Microsoft

String Dynamic Programming Stack Greedy

#606

Rank

#1566EasyFrequency: 7.3%

Check If a Word Occurs As a Prefix of Any Word in a Sentence

Asked at Microsoft

Two Pointers String String Matching

#607

Rank

#1652MediumFrequency: 7.3%

Minimum Suffix Flips

Asked at Microsoft

#608

Rank

#3403MediumFrequency: 7.3%

Minimum Substring Partition of Equal Character Frequency

Asked at Microsoft

Hash Table String Dynamic Programming Counting

#609

Rank

#1561MediumFrequency: 7.3%

Rearrange Words in a Sentence

Asked at Microsoft

#610

Rank

#2444MediumFrequency: 7.3%

Longest Ideal Subsequence

Asked at Microsoft

Hash Table String Dynamic Programming

#611

Rank

#3569MediumFrequency: 7.3%

Count of Substrings Containing Every Vowel and K Consonants II

Asked at Microsoft

Hash Table String Sliding Window

#612

Rank

#2251HardFrequency: 7.3%

Number of Ways to Divide a Long Corridor

Asked at Microsoft

Math String Dynamic Programming

#613

Rank

#4186EasyFrequency: 7.3%

Count Residue Prefixes

Asked at Microsoft

Hash Table String

#614

Rank

#3245MediumFrequency: 7.3%

Find Beautiful Indices in the Given Array I

Asked at Microsoft

Two Pointers String Binary Search Rolling Hash String Matching Hash Function Z Algorithm Knuth–Morris–Pratt Algorithm Boyer–Moore String-Search Algorithm

#615

Rank

#1746EasyFrequency: 7.3%

Largest Substring Between Two Equal Characters

Asked at Microsoft

Hash Table String

#616

Rank

#2391EasyFrequency: 7.3%

Strong Password Checker II

Asked at Microsoft

#617

Rank

#3238HardFrequency: 7.3%

Minimum Cost to Convert String II

Asked at Microsoft

Array String Dynamic Programming Graph Theory Trie Shortest Path

#618

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#2999EasyFrequency: 7.3%

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Asked at Microsoft

#619

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#2978MediumFrequency: 7.3%

Check if Strings Can be Made Equal With Operations II

Asked at Microsoft

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#620

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#1904EasyFrequency: 7.3%

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Asked at Microsoft

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#621

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#2187MediumFrequency: 7.3%

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#622

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#720MediumFrequency: 7.3%

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#623

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#855HardFrequency: 7.2%

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#624

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#3553EasyFrequency: 7.2%

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#625

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#2027MediumFrequency: 7.2%

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Array Two Pointers String Binary Search

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#2053EasyFrequency: 7.2%

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#627

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#3636EasyFrequency: 7.2%

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#628

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#1885MediumFrequency: 5.5%

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Asked at Google

#629

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#824EasyFrequency: 5.5%

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#630

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#1429HardFrequency: 5.5%

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#631

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#2727EasyFrequency: 5.5%

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#632

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#3055EasyFrequency: 5.5%

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#633

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#2154EasyFrequency: 5.5%

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#634

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#635

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#1823EasyFrequency: 5.5%

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#1261MediumFrequency: 5.5%

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#637

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#1797EasyFrequency: 5.5%

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#638

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#3540MediumFrequency: 5.5%

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#639

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#2260EasyFrequency: 5.5%

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#640

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#1490EasyFrequency: 5.5%

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#641

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#467MediumFrequency: 5.5%

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#642

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#466HardFrequency: 5.5%

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#643

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#3462MediumFrequency: 5.5%

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#644

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#3588HardFrequency: 5.5%

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#645

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#2130MediumFrequency: 5.5%

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#646

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#2825EasyFrequency: 5.5%

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#647

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#2317MediumFrequency: 5.5%

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#648

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#488HardFrequency: 5.5%

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#649

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#3934EasyFrequency: 5.5%

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#650

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#3877MediumFrequency: 5.5%

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#651

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#3811EasyFrequency: 5.5%

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#652

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#4216EasyFrequency: 5.5%

Weighted Word Mapping

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#653

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#822EasyFrequency: 5.5%

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#654

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#3247MediumFrequency: 5%

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#655

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#3552HardFrequency: 5%

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#656

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#3533EasyFrequency: 5%

Snake in Matrix

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#657

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#3502MediumFrequency: 5%

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Hash Table String Sliding Window

#658

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#3487MediumFrequency: 5%

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#659

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#3309EasyFrequency: 5%

Count Prefix and Suffix Pairs I

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Array String Trie Rolling Hash String Matching Hash Function

#660

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#1433HardFrequency: 5%

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Array Hash Table String Design Trie

#661

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#3591MediumFrequency: 5%

Shift Distance Between Two Strings

Asked at Google

Array String Prefix Sum

#662

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#499HardFrequency: 5%

The Maze III

Asked at Google

Array String Depth-First Search Breadth-First Search Graph Theory Heap (Priority Queue)Matrix Shortest Path Dijkstra's Algorithm Heuristic Search A* Search

#663

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#3360MediumFrequency: 5%

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Hash Table String Greedy Sorting Counting

#664

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#3793MediumFrequency: 5%

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#665

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#2113MediumFrequency: 5%

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Array String Divide and Conquer Sorting Heap (Priority Queue)Quickselect

#666

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#1517HardFrequency: 5%

Restore The Array

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String Dynamic Programming

#667

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#1472EasyFrequency: 5%

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#668

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#3774HardFrequency: 5%

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Math String Combinatorics Number Theory

#669

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#2275HardFrequency: 5%

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String Sliding Window Rolling Hash Hash Function

#670

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#3634MediumFrequency: 5%

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Asked at Google

Hash Table String Stack Simulation

#671

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#3808HardFrequency: 5%

Longest Palindrome After Substring Concatenation II

Asked at Google

Two Pointers String Dynamic Programming

#672

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#2589EasyFrequency: 5%

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#673

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#1430EasyFrequency: 5%

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#674

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#4275EasyFrequency: 5%

Traffic Signal Color

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#675

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#3696HardFrequency: 5%

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String Dynamic Programming

#676

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#4265MediumFrequency: 5%

Longest Balanced Substring After One Swap

Asked at Google

Hash Table String Prefix Sum

#677

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#858MediumFrequency: 5%

Masking Personal Information

Asked at Google

#678

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#3930HardFrequency: 5%

Longest Palindromic Path in Graph

Asked at Google

String Dynamic Programming Bit Manipulation Graph Theory Bitmask

#679

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#3570MediumFrequency: 5%

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Hash Table String Sliding Window

#680

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#4140HardFrequency: 5%

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Asked at Google

Hash Table Math String Divide and Conquer Stack

#681

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#2828MediumFrequency: 5%

Lexicographically Smallest String After Substring Operation

Asked at Amazon

#682

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#3312EasyFrequency: 5%

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#683

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#3771MediumFrequency: 5%

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Asked at Amazon

Hash Table String Dynamic Programming Greedy Sorting

#684

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#1994MediumFrequency: 5%

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#685

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#3800MediumFrequency: 5%

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Asked at Amazon

#686

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#3709EasyFrequency: 5%

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#687

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#3573MediumFrequency: 5%

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Asked at Amazon

Hash Table String Sliding Window

#688

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#3426EasyFrequency: 5%

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Asked at Amazon

String Simulation

#689

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#2011MediumFrequency: 5%

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#690

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#1949MediumFrequency: 5%

Implement Trie II (Prefix Tree)

Asked at Amazon

Hash Table String Design Trie

#691

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#2476EasyFrequency: 5%

Check Distances Between Same Letters

Asked at Amazon

Array Hash Table String

#692

Rank

#2816EasyFrequency: 5%

Lexicographically Smallest Palindrome

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Two Pointers String Greedy

#693

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#4087MediumFrequency: 5%

Maximum Substrings With Distinct Start

Asked at Amazon

Hash Table String

#694

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#2605HardFrequency: 5%

Count Anagrams

Asked at Amazon

Hash Table Math String Combinatorics Counting Fermat's Little Theorem

#695

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#3142MediumFrequency: 5%

Longest Unequal Adjacent Groups Subsequence II

Array String Dynamic Programming

#696

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#4086HardFrequency: 5%

Lexicographically Smallest String After Deleting Duplicate Characters

Hash Table String Stack Greedy Monotonic Stack

#697

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#1944EasyFrequency: 5%

Truncate Sentence

#698

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