Top 100 Interview Questions

Array Hash Table

Rank

#3594MediumFrequency: 100%High Priority

Identify the Largest Outlier in an Array

Array Hash Table Counting Enumeration

Rank

#3655MediumFrequency: 100%High Priority

Digit Operations to Make Two Integers Equal

Math Graph Heap (Priority Queue)Number Theory Shortest Path

Rank

#1371MediumFrequency: 100%High Priority

Minimum Remove to Make Valid Parentheses

Rank

#1352HardFrequency: 100%High Priority

Maximum Profit in Job Scheduling

Array Binary Search Dynamic Programming Sorting

Rank

#232EasyFrequency: 100%High Priority

Implement Queue using Stacks

Stack Design Queue

Rank

#3613MediumFrequency: 100%High Priority

Maximize Amount After Two Days of Conversions

Array String Depth-First Search Breadth-First Search Graph

Rank

#716HardFrequency: 100%High Priority

Max Stack

Linked List Stack Design Doubly-Linked List Ordered Set

Rank

#1085MediumFrequency: 100%High Priority

The Earliest Moment When Everyone Become Friends

Array Union Find Sorting

Rank

#392EasyFrequency: 100%High Priority

Is Subsequence

Two Pointers String Dynamic Programming

#10

Rank

#64MediumFrequency: 100%High Priority

Minimum Path Sum

Array Dynamic Programming Matrix

#11

Rank

#817EasyFrequency: 100%High Priority

Design HashMap

Asked at DoorDash

Array Hash Table Linked List Design Hash Function

#12

Rank

#322MediumFrequency: 100%High Priority

Coin Change

Array Dynamic Programming Breadth-First Search

#13

Rank

#2383EasyFrequency: 100%High Priority

Add Two Integers

#14

Rank

#42HardFrequency: 100%High Priority

Trapping Rain Water

Array Two Pointers Dynamic Programming Stack Monotonic Stack

#15

Rank

#3681MediumFrequency: 100%High Priority

Maximum Area Rectangle With Point Constraints I

Array Math Binary Indexed Tree Segment Tree Geometry+2 more

#16

Rank

#1056MediumFrequency: 100%High Priority

Capacity To Ship Packages Within D Days

#17

Rank

#694MediumFrequency: 98%High Priority

Number of Distinct Islands

Hash Table Depth-First Search Breadth-First Search Union Find Hash Function

#18

Rank

#314MediumFrequency: 97%High Priority

Binary Tree Vertical Order Traversal

Hash Table Tree Depth-First Search Breadth-First Search Sorting+1 more

#19

Rank

#227MediumFrequency: 96%High Priority

Basic Calculator II

Math String Stack

#20

Rank

#680EasyFrequency: 95%High Priority

Valid Palindrome II

Two Pointers String Greedy

#21

Rank

#833HardFrequency: 95%High Priority

Bus Routes

Array Hash Table Breadth-First Search

#22

Rank

#739MediumFrequency: 94%High Priority

Daily Temperatures

#23

Rank

#415EasyFrequency: 94%High Priority

Add Strings

Math String Simulation

#24

Rank

#957MediumFrequency: 94%High Priority

Minimum Add to Make Parentheses Valid

String Stack Greedy

#25

Rank

#2891MediumFrequency: 93%High Priority

Maximum Beauty of an Array After Applying Operation

Array Binary Search Sliding Window Sorting

#26

Rank

#152MediumFrequency: 93%High Priority

Maximum Product Subarray

#27

Rank

#2MediumFrequency: 93%High Priority

Add Two Numbers

Linked List Math Recursion

#28

Rank

#84HardFrequency: 93%High Priority

Largest Rectangle in Histogram

#29

Rank

#234EasyFrequency: 93%High Priority

Palindrome Linked List

Linked List Two Pointers Stack Recursion

#30

Rank

#3639MediumFrequency: 93%High Priority

Zero Array Transformation I

Array Prefix Sum

#31

Rank

#88EasyFrequency: 92%High Priority

Merge Sorted Array

#32

Rank

#215MediumFrequency: 92%High Priority

Kth Largest Element in an Array

Array Divide and Conquer Sorting Heap (Priority Queue)Quickselect

#33

Rank

#19MediumFrequency: 92%High Priority

Remove Nth Node From End of List

Linked List Two Pointers

#34

Rank

#1790MediumFrequency: 91%High Priority

Lowest Common Ancestor of a Binary Tree III

Hash Table Two Pointers Tree Binary Tree

#35

Rank

#129MediumFrequency: 91%High Priority

Sum Root to Leaf Numbers

#36

Rank

#1046MediumFrequency: 91%High Priority

Max Consecutive Ones III

Array Binary Search Sliding Window Prefix Sum

#37

Rank

#65HardFrequency: 91%High Priority

Valid Number

#38

Rank

#1423MediumFrequency: 91%High Priority

Maximum Number of Occurrences of a Substring

#39

Rank

#122MediumFrequency: 90%High Priority

Best Time to Buy and Sell Stock II

Array Dynamic Programming Greedy

#40

Rank

#20EasyFrequency: 90%High Priority

Valid Parentheses

#41

Rank

#121EasyFrequency: 89%High Priority

Best Time to Buy and Sell Stock

#42

Rank

#136EasyFrequency: 89%High Priority

Single Number

Array Bit Manipulation

#43

Rank

#852MediumFrequency: 89%High Priority

Friends Of Appropriate Ages

Array Two Pointers Binary Search Sorting

#44

Rank

#146MediumFrequency: 88%High Priority

LRU Cache

#45

Rank

#364MediumFrequency: 88%High Priority

Nested List Weight Sum II

Stack Depth-First Search Breadth-First Search

#46

Rank

#7MediumFrequency: 88%High Priority

Reverse Integer

#47

Rank

#6MediumFrequency: 88%High Priority

Zigzag Conversion

#48

Rank

#408EasyFrequency: 87%High Priority

Valid Word Abbreviation

#49

Rank

#912MediumFrequency: 87%High Priority

Random Pick with Weight

Array Math Binary Search Prefix Sum Randomized

#50

Rank

#998MediumFrequency: 87%High Priority

Check Completeness of a Binary Tree

Tree Breadth-First Search Binary Tree

#51

Rank

#394MediumFrequency: 87%High Priority

Decode String

String Stack Recursion

#52

Rank

#621MediumFrequency: 85%High Priority

Task Scheduler

Array Hash Table Greedy Sorting Heap (Priority Queue)+1 more

#53

Rank

#50MediumFrequency: 85%High Priority

Pow(x, n)

Math Recursion

#54

Rank

#162MediumFrequency: 85%High Priority

Find Peak Element

#55

Rank

#1019EasyFrequency: 85%High Priority

Squares of a Sorted Array

#56

Rank

#134MediumFrequency: 85%High Priority

Gas Station

Array Greedy

#57

Rank

#3MediumFrequency: 84%High Priority

Longest Substring Without Repeating Characters

#58

Rank

#339MediumFrequency: 84%High Priority

Nested List Weight Sum

Depth-First Search Breadth-First Search

#59

Rank

#366MediumFrequency: 84%High Priority

Find Leaves of Binary Tree

#60

Rank

#124HardFrequency: 84%High Priority

Binary Tree Maximum Path Sum

Dynamic Programming Tree Depth-First Search Binary Tree

#61

Rank

#387EasyFrequency: 83%High Priority

First Unique Character in a String

Hash Table String Queue Counting

#62

Rank

#1330MediumFrequency: 83%High Priority

Longest Arithmetic Subsequence of Given Difference

Array Hash Table Dynamic Programming

#63

Rank

#1108MediumFrequency: 83%High Priority

Analyze User Website Visit Pattern

Array Hash Table Sorting

#64

Rank

#772MediumFrequency: 83%High Priority

Construct Quad Tree

Array Divide and Conquer Tree Matrix

#65

Rank

#3654MediumFrequency: 83%High Priority

Minimum Array Sum

#66

Rank

#200MediumFrequency: 82%High Priority

Number of Islands

Array Depth-First Search Breadth-First Search Union Find Matrix

#67

Rank

#424MediumFrequency: 82%High Priority

Longest Repeating Character Replacement

#68

Rank

#398MediumFrequency: 82%High Priority

Random Pick Index

Hash Table Math Reservoir Sampling Randomized

#69

Rank

#1908EasyFrequency: 82%High Priority

Recyclable and Low Fat Products

Database

#70

Rank

#1014MediumFrequency: 82%High Priority

K Closest Points to Origin

Array Math Divide and Conquer Geometry Sorting+2 more

#71

Rank

#273HardFrequency: 82%High Priority

Integer to English Words

Math String Recursion

#72

Rank

#141EasyFrequency: 82%High Priority

Linked List Cycle

Hash Table Linked List Two Pointers

#73

Rank

#432HardFrequency: 82%High Priority

All O`one Data Structure

#74

Rank

#560MediumFrequency: 81%High Priority

Subarray Sum Equals K

Array Hash Table Prefix Sum

#75

Rank

#348MediumFrequency: 81%High Priority

Design Tic-Tac-Toe

Array Hash Table Design Matrix Simulation

#76

Rank

#733EasyFrequency: 81%High Priority

Flood Fill

Array Depth-First Search Breadth-First Search Matrix

#77

Rank

#1894EasyFrequency: 80%High Priority

Merge Strings Alternately

#78

Rank

#1566EasyFrequency: 80%High Priority

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

Two Pointers String String Matching

#79

Rank

#151MediumFrequency: 80%High Priority

Reverse Words in a String

#80

Rank

#27EasyFrequency: 80%High Priority

Remove Element

Array Two Pointers

#81

Rank

#104EasyFrequency: 80%High Priority

Maximum Depth of Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#82

Rank

#53MediumFrequency: 79%High Priority

Maximum Subarray

Array Divide and Conquer Dynamic Programming

#83

Rank

#70EasyFrequency: 79%High Priority

Climbing Stairs

Math Dynamic Programming Memoization

#84

Rank

#236MediumFrequency: 79%High Priority

Lowest Common Ancestor of a Binary Tree

#85

Rank

#269HardFrequency: 79%High Priority

Alien Dictionary

Array String Depth-First Search Breadth-First Search Graph+1 more

#86

Rank

#305HardFrequency: 79%High Priority

Number of Islands II

Array Hash Table Union Find

#87

Rank

#362MediumFrequency: 79%High Priority

Design Hit Counter

Array Binary Search Design Queue Data Stream

#88

Rank

#380MediumFrequency: 79%High Priority

Insert Delete GetRandom O(1)

Array Hash Table Math Design Randomized

#89

Rank

#1966MediumFrequency: 79%High Priority

Frequency of the Most Frequent Element

Array Binary Search Greedy Sliding Window Sorting+1 more

#90

Rank

#109MediumFrequency: 79%High Priority

Convert Sorted List to Binary Search Tree

Linked List Divide and Conquer Tree Binary Search Tree Binary Tree

#91

Rank

#329HardFrequency: 79%High Priority

Longest Increasing Path in a Matrix

Array Dynamic Programming Depth-First Search Breadth-First Search Graph+3 more

#92

Rank

#4HardFrequency: 79%High Priority

Median of Two Sorted Arrays

Array Binary Search Divide and Conquer

#93

Rank

#166MediumFrequency: 79%High Priority

Fraction to Recurring Decimal

Hash Table Math String

#94

Rank

#125EasyFrequency: 78%High Priority

Valid Palindrome

#95

Rank

#74MediumFrequency: 78%High Priority

Search a 2D Matrix

Array Binary Search Matrix

#96

Rank

#2809EasyFrequency: 77%High Priority

Create Hello World Function

#97

Rank

#356MediumFrequency: 77%High Priority

Line Reflection

Array Hash Table Math

#98

Rank

#199MediumFrequency: 76%High Priority

Binary Tree Right Side View

Tree Depth-First Search Breadth-First Search Binary Tree

#99

Rank

#347MediumFrequency: 76%High Priority

Top K Frequent Elements

Array Hash Table Divide and Conquer Sorting Heap (Priority Queue)+3 more

#100

Rank

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Top 100 Interview Questions

Essential collection of 100 coding problems that appear most often in technical interviews.

100

Total Problems

Easy

Medium

Hard

88%

Avg Frequency

Most Common Topics

Companies Asking These Questions

Meta (16)Salesforce (12)Flipkart (10)Oracle (9)Infosys (9)Microsoft (6)

Problems in This Collection

#1EasyFrequency: 100%High Priority

Two Sum

Array Hash Table

Rank

#3594MediumFrequency: 100%High Priority

Identify the Largest Outlier in an Array

Array Hash Table Counting Enumeration

Rank

#3655MediumFrequency: 100%High Priority

Digit Operations to Make Two Integers Equal

Math Graph Heap (Priority Queue)Number Theory Shortest Path

Rank

#1371MediumFrequency: 100%High Priority

Minimum Remove to Make Valid Parentheses

Rank

#1352HardFrequency: 100%High Priority

Maximum Profit in Job Scheduling

Array Binary Search Dynamic Programming Sorting

Rank

#232EasyFrequency: 100%High Priority

Implement Queue using Stacks

Stack Design Queue

Rank

#3613MediumFrequency: 100%High Priority

Maximize Amount After Two Days of Conversions

Array String Depth-First Search Breadth-First Search Graph

Rank

#716HardFrequency: 100%High Priority

Max Stack

Linked List Stack Design Doubly-Linked List Ordered Set

Rank

#1085MediumFrequency: 100%High Priority

The Earliest Moment When Everyone Become Friends

Array Union Find Sorting

Rank

#392EasyFrequency: 100%High Priority

Is Subsequence

Two Pointers String Dynamic Programming

#10

Rank

#64MediumFrequency: 100%High Priority

Minimum Path Sum

Array Dynamic Programming Matrix

#11

Rank

#817EasyFrequency: 100%High Priority

Design HashMap

Asked at DoorDash

Array Hash Table Linked List Design Hash Function

#12

Rank

#322MediumFrequency: 100%High Priority

Coin Change

Array Dynamic Programming Breadth-First Search

#13

Rank

#2383EasyFrequency: 100%High Priority

Add Two Integers

#14

Rank

#42HardFrequency: 100%High Priority

Trapping Rain Water

Array Two Pointers Dynamic Programming Stack Monotonic Stack

#15

Rank

#3681MediumFrequency: 100%High Priority

Maximum Area Rectangle With Point Constraints I

Array Math Binary Indexed Tree Segment Tree Geometry+2 more

#16

Rank

#1056MediumFrequency: 100%High Priority

Capacity To Ship Packages Within D Days

#17

Rank

#694MediumFrequency: 98%High Priority

Number of Distinct Islands

Hash Table Depth-First Search Breadth-First Search Union Find Hash Function

#18

Rank

#314MediumFrequency: 97%High Priority

Binary Tree Vertical Order Traversal

Hash Table Tree Depth-First Search Breadth-First Search Sorting+1 more

#19

Rank

#227MediumFrequency: 96%High Priority

Basic Calculator II

Math String Stack

#20

Rank

#680EasyFrequency: 95%High Priority

Valid Palindrome II

Two Pointers String Greedy

#21

Rank

#833HardFrequency: 95%High Priority

Bus Routes

Array Hash Table Breadth-First Search

#22

Rank

#739MediumFrequency: 94%High Priority

Daily Temperatures

#23

Rank

#415EasyFrequency: 94%High Priority

Add Strings

Math String Simulation

#24

Rank

#957MediumFrequency: 94%High Priority

Minimum Add to Make Parentheses Valid

String Stack Greedy

#25

Rank

#2891MediumFrequency: 93%High Priority

Maximum Beauty of an Array After Applying Operation

Array Binary Search Sliding Window Sorting

#26

Rank

#152MediumFrequency: 93%High Priority

Maximum Product Subarray

#27

Rank

#2MediumFrequency: 93%High Priority

Add Two Numbers

Linked List Math Recursion

#28

Rank

#84HardFrequency: 93%High Priority

Largest Rectangle in Histogram

#29

Rank

#234EasyFrequency: 93%High Priority

Palindrome Linked List

Linked List Two Pointers Stack Recursion

#30

Rank

#3639MediumFrequency: 93%High Priority

Zero Array Transformation I

Array Prefix Sum

#31

Rank

#88EasyFrequency: 92%High Priority

Merge Sorted Array

#32

Rank

#215MediumFrequency: 92%High Priority

Kth Largest Element in an Array

Array Divide and Conquer Sorting Heap (Priority Queue)Quickselect

#33

Rank

#19MediumFrequency: 92%High Priority

Remove Nth Node From End of List

Linked List Two Pointers

#34

Rank

#1790MediumFrequency: 91%High Priority

Lowest Common Ancestor of a Binary Tree III

Hash Table Two Pointers Tree Binary Tree

#35

Rank

#129MediumFrequency: 91%High Priority

Sum Root to Leaf Numbers

#36

Rank

#1046MediumFrequency: 91%High Priority

Max Consecutive Ones III

Array Binary Search Sliding Window Prefix Sum

#37

Rank

#65HardFrequency: 91%High Priority

Valid Number

#38

Rank

#1423MediumFrequency: 91%High Priority

Maximum Number of Occurrences of a Substring

#39

Rank

#122MediumFrequency: 90%High Priority

Best Time to Buy and Sell Stock II

Array Dynamic Programming Greedy

#40

Rank

#20EasyFrequency: 90%High Priority

Valid Parentheses

#41

Rank

#121EasyFrequency: 89%High Priority

Best Time to Buy and Sell Stock

#42

Rank

#136EasyFrequency: 89%High Priority

Single Number

Array Bit Manipulation

#43

Rank

#852MediumFrequency: 89%High Priority

Friends Of Appropriate Ages

Array Two Pointers Binary Search Sorting

#44

Rank

#146MediumFrequency: 88%High Priority

LRU Cache

#45

Rank

#364MediumFrequency: 88%High Priority

Nested List Weight Sum II

Stack Depth-First Search Breadth-First Search

#46

Rank

#7MediumFrequency: 88%High Priority

Reverse Integer

#47

Rank

#6MediumFrequency: 88%High Priority

Zigzag Conversion

#48

Rank

#408EasyFrequency: 87%High Priority

Valid Word Abbreviation

#49

Rank

#912MediumFrequency: 87%High Priority

Random Pick with Weight

Array Math Binary Search Prefix Sum Randomized

#50

Rank

#998MediumFrequency: 87%High Priority

Check Completeness of a Binary Tree

Tree Breadth-First Search Binary Tree

#51

Rank

#394MediumFrequency: 87%High Priority

Decode String

String Stack Recursion

#52

Rank

#621MediumFrequency: 85%High Priority

Task Scheduler

Array Hash Table Greedy Sorting Heap (Priority Queue)+1 more

#53

Rank

#50MediumFrequency: 85%High Priority

Pow(x, n)

Math Recursion

#54

Rank

#162MediumFrequency: 85%High Priority

Find Peak Element

#55

Rank

#1019EasyFrequency: 85%High Priority

Squares of a Sorted Array

#56

Rank

#134MediumFrequency: 85%High Priority

Gas Station

Array Greedy

#57

Rank

#3MediumFrequency: 84%High Priority

Longest Substring Without Repeating Characters

#58

Rank

#339MediumFrequency: 84%High Priority

Nested List Weight Sum

Depth-First Search Breadth-First Search

#59

Rank

#366MediumFrequency: 84%High Priority

Find Leaves of Binary Tree

#60

Rank

#124HardFrequency: 84%High Priority

Binary Tree Maximum Path Sum

Dynamic Programming Tree Depth-First Search Binary Tree

#61

Rank

#387EasyFrequency: 83%High Priority

First Unique Character in a String

Hash Table String Queue Counting

#62

Rank

#1330MediumFrequency: 83%High Priority

Longest Arithmetic Subsequence of Given Difference

Array Hash Table Dynamic Programming

#63

Rank

#1108MediumFrequency: 83%High Priority

Analyze User Website Visit Pattern

Array Hash Table Sorting

#64

Rank

#772MediumFrequency: 83%High Priority

Construct Quad Tree

Array Divide and Conquer Tree Matrix

#65

Rank

#3654MediumFrequency: 83%High Priority

Minimum Array Sum

#66

Rank

#200MediumFrequency: 82%High Priority

Number of Islands

Array Depth-First Search Breadth-First Search Union Find Matrix

#67

Rank

#424MediumFrequency: 82%High Priority

Longest Repeating Character Replacement

#68

Rank

#398MediumFrequency: 82%High Priority

Random Pick Index

Hash Table Math Reservoir Sampling Randomized

#69

Rank

#1908EasyFrequency: 82%High Priority

Recyclable and Low Fat Products

Database

#70

Rank

#1014MediumFrequency: 82%High Priority

K Closest Points to Origin

Array Math Divide and Conquer Geometry Sorting+2 more

#71

Rank

#273HardFrequency: 82%High Priority

Integer to English Words

Math String Recursion

#72

Rank

#141EasyFrequency: 82%High Priority

Linked List Cycle

Hash Table Linked List Two Pointers

#73

Rank

#432HardFrequency: 82%High Priority

All O`one Data Structure

#74

Rank

#560MediumFrequency: 81%High Priority

Subarray Sum Equals K

Array Hash Table Prefix Sum

#75

Rank

#348MediumFrequency: 81%High Priority

Design Tic-Tac-Toe

Array Hash Table Design Matrix Simulation

#76

Rank

#733EasyFrequency: 81%High Priority

Flood Fill

Array Depth-First Search Breadth-First Search Matrix

#77

Rank

#1894EasyFrequency: 80%High Priority

Merge Strings Alternately

#78

Rank

#1566EasyFrequency: 80%High Priority

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

Two Pointers String String Matching

#79

Rank

#151MediumFrequency: 80%High Priority

Reverse Words in a String

#80

Rank

#27EasyFrequency: 80%High Priority

Remove Element

Array Two Pointers

#81

Rank

#104EasyFrequency: 80%High Priority

Maximum Depth of Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#82

Rank

#53MediumFrequency: 79%High Priority

Maximum Subarray

Array Divide and Conquer Dynamic Programming

#83

Rank

#70EasyFrequency: 79%High Priority

Climbing Stairs

Math Dynamic Programming Memoization

#84

Rank

#236MediumFrequency: 79%High Priority

Lowest Common Ancestor of a Binary Tree

#85

Rank

#269HardFrequency: 79%High Priority

Alien Dictionary

Array String Depth-First Search Breadth-First Search Graph+1 more

#86

Rank

#305HardFrequency: 79%High Priority

Number of Islands II

Array Hash Table Union Find

#87

Rank

#362MediumFrequency: 79%High Priority

Design Hit Counter

Array Binary Search Design Queue Data Stream

#88

Rank

#380MediumFrequency: 79%High Priority

Insert Delete GetRandom O(1)

Array Hash Table Math Design Randomized

#89

Rank

#1966MediumFrequency: 79%High Priority

Frequency of the Most Frequent Element

Array Binary Search Greedy Sliding Window Sorting+1 more

#90

Rank

#109MediumFrequency: 79%High Priority

Convert Sorted List to Binary Search Tree

Linked List Divide and Conquer Tree Binary Search Tree Binary Tree

#91

Rank

#329HardFrequency: 79%High Priority

Longest Increasing Path in a Matrix

Array Dynamic Programming Depth-First Search Breadth-First Search Graph+3 more

#92

Rank

#4HardFrequency: 79%High Priority

Median of Two Sorted Arrays

Array Binary Search Divide and Conquer

#93

Rank

#166MediumFrequency: 79%High Priority

Fraction to Recurring Decimal

Hash Table Math String

#94

Rank

#125EasyFrequency: 78%High Priority

Valid Palindrome

#95

Rank

#74MediumFrequency: 78%High Priority

Search a 2D Matrix

Array Binary Search Matrix

#96

Rank

#2809EasyFrequency: 77%High Priority

Create Hello World Function

#97

Rank

#356MediumFrequency: 77%High Priority

Line Reflection

Array Hash Table Math

#98

Rank

#199MediumFrequency: 76%High Priority

Binary Tree Right Side View

Tree Depth-First Search Breadth-First Search Binary Tree

#99

Rank

#347MediumFrequency: 76%High Priority

Top K Frequent Elements

Array Hash Table Divide and Conquer Sorting Heap (Priority Queue)+3 more

#100

Rank

Other Collections

Most Frequent Interview Questions

The top 50 most frequently asked coding interview questions across all major tech companies.

Beginner-Friendly Interview Questions

Easy to medium difficulty problems perfect for interview preparation beginners.

75 problems →

Advanced Interview Problems

Challenging hard problems asked at top-tier tech companies for senior positions.