Beginner-Friendly Interview Questions

Hash Table Linked List Design Doubly-Linked List

Rank

#146MediumFrequency: 100%High Priority

LRU Cache

Asked at Apple

Rank

#2710MediumFrequency: 100%High Priority

Minimum Operations to Reduce an Integer to 0

Dynamic Programming Greedy Bit Manipulation

Rank

#286MediumFrequency: 100%High Priority

Walls and Gates

Rank

#1538MediumFrequency: 100%High Priority

Maximum Points You Can Obtain from Cards

Array Sliding Window Prefix Sum

Rank

#6MediumFrequency: 100%High Priority

Zigzag Conversion

String

Rank

#362MediumFrequency: 100%High Priority

Design Hit Counter

Array Binary Search Design Queue Data Stream

Rank

#752MediumFrequency: 97.6%High Priority

IP to CIDR

String Bit Manipulation

Rank

#200MediumFrequency: 97.3%High Priority

Number of Islands

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

#10

Rank

#408EasyFrequency: 96.8%High Priority

Valid Word Abbreviation

#11

Rank

#364MediumFrequency: 95.4%High Priority

Nested List Weight Sum II

Stack Depth-First Search Breadth-First Search

#12

Rank

#680EasyFrequency: 95.1%High Priority

Valid Palindrome II

Two Pointers String Greedy

#13

Rank

#1306EasyFrequency: 94.7%High Priority

Minimum Absolute Difference

Array Sorting

#14

Rank

#1549MediumFrequency: 94.4%High Priority

Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit

Array Queue Sliding Window Heap (Priority Queue)Ordered Set+1 more

#15

Rank

#348MediumFrequency: 93.6%High Priority

Design Tic-Tac-Toe

Array Hash Table Design Matrix Simulation

#16

Rank

#314MediumFrequency: 93.4%High Priority

Binary Tree Vertical Order Traversal

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

#17

Rank

#215MediumFrequency: 93.3%High Priority

Kth Largest Element in an Array

Array Divide and Conquer Sorting Heap (Priority Queue)Quickselect

#18

Rank

#3MediumFrequency: 92.8%High Priority

Longest Substring Without Repeating Characters

#19

Rank

#300MediumFrequency: 89.7%High Priority

Longest Increasing Subsequence

Array Binary Search Dynamic Programming Longest Increasing Subsequence

#20

Rank

#227MediumFrequency: 89.3%High Priority

Basic Calculator II

Math String Stack

#21

Rank

#1790MediumFrequency: 88.5%High Priority

Lowest Common Ancestor of a Binary Tree III

Hash Table Two Pointers Tree Binary Tree Binary Lifting+1 more

#22

Rank

#443MediumFrequency: 88.1%High Priority

String Compression

#23

Rank

#339MediumFrequency: 87.9%High Priority

Nested List Weight Sum

Depth-First Search Breadth-First Search

#24

Rank

#912MediumFrequency: 87.7%High Priority

Random Pick with Weight

Array Math Binary Search Prefix Sum Randomized

#25

Rank

#560MediumFrequency: 87.2%High Priority

Subarray Sum Equals K

Array Hash Table Prefix Sum

#26

Rank

#772MediumFrequency: 87%High Priority

Construct Quad Tree

Array Divide and Conquer Tree Matrix

#27

Rank

#543EasyFrequency: 86.8%High Priority

Diameter of Binary Tree

Tree Depth-First Search Binary Tree DP on Trees

#28

Rank

#694MediumFrequency: 86.6%High Priority

Number of Distinct Islands

Array Hash Table Depth-First Search Breadth-First Search Union-Find+3 more

#29

Rank

#236MediumFrequency: 86.4%High Priority

Lowest Common Ancestor of a Binary Tree

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

#30

Rank

#88EasyFrequency: 86.3%High Priority

Merge Sorted Array

#31

Rank

#210MediumFrequency: 85.9%High Priority

Course Schedule II

Depth-First Search Breadth-First Search Graph Theory Topological Sort

#32

Rank

#162MediumFrequency: 85.8%High Priority

Find Peak Element

Array Binary Search

#33

Rank

#1019EasyFrequency: 85.8%High Priority

Squares of a Sorted Array

#34

Rank

#251MediumFrequency: 85.6%High Priority

Flatten 2D Vector

Array Two Pointers Design Iterator

#35

Rank

#199MediumFrequency: 85.4%High Priority

Binary Tree Right Side View

Tree Depth-First Search Breadth-First Search Binary Tree

#36

Rank

#56MediumFrequency: 84.6%High Priority

Merge Intervals

Array Sorting Quicksort

#37

Rank

#438MediumFrequency: 84.4%High Priority

Find All Anagrams in a String

#38

Rank

#3876MediumFrequency: 84.3%High Priority

Transform Array to All Equal Elements

Array Greedy

#39

Rank

#50MediumFrequency: 84.1%High Priority

Pow(x, n)

Math Recursion

#40

Rank

#121EasyFrequency: 83.8%High Priority

Best Time to Buy and Sell Stock

#41

Rank

#253MediumFrequency: 83.8%High Priority

Meeting Rooms II

Array Two Pointers Greedy Sorting Heap (Priority Queue)+1 more

#42

Rank

#71MediumFrequency: 83.7%High Priority

Simplify Path

#43

Rank

#2217MediumFrequency: 83.7%High Priority

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

String Tree Depth-First Search Binary Tree Binary Lifting+1 more

#44

Rank

#198MediumFrequency: 83.7%High Priority

House Robber

#45

Rank

#1366MediumFrequency: 83.2%High Priority

First Unique Number

Array Hash Table Design Queue Data Stream

#46

Rank

#1046MediumFrequency: 83.2%High Priority

Max Consecutive Ones III

Array Binary Search Sliding Window Prefix Sum

#47

Rank

#1112EasyFrequency: 82.7%High Priority

Find Words That Can Be Formed by Characters

Array Hash Table String Counting

#48

Rank

#125EasyFrequency: 82.6%High Priority

Valid Palindrome

#49

Rank

#1909MediumFrequency: 82.6%High Priority

Buildings With an Ocean View

Array Stack Monotonic Stack

#50

Rank

#1397MediumFrequency: 82.5%High Priority

Search Suggestions System

Array String Binary Search Trie Sorting+1 more

#51

Rank

#1190MediumFrequency: 82.4%High Priority

Smallest Common Region

Array Hash Table String Tree Depth-First Search+3 more

#52

Rank

#207MediumFrequency: 82.3%High Priority

Course Schedule

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

#53

Rank

#230MediumFrequency: 82.3%High Priority

Kth Smallest Element in a BST

Tree Depth-First Search Binary Search Tree Binary Tree

#54

Rank

#244MediumFrequency: 82.3%High Priority

Shortest Word Distance II

Array Hash Table Two Pointers String Design

#55

Rank

#3231MediumFrequency: 82%High Priority

Minimum Number of Coins to be Added

Array Greedy Sorting

#56

Rank

#1036MediumFrequency: 82%High Priority

Rotting Oranges

Array Hash Table String Sorting

#57

Rank

#49MediumFrequency: 81.6%High Priority

Group Anagrams

Asked at Oracle

#58

Rank

#2MediumFrequency: 81.4%High Priority

Add Two Numbers

Linked List Math Recursion

#59

Rank

#347MediumFrequency: 81.3%High Priority

Top K Frequent Elements

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

#60

Rank

#53MediumFrequency: 81.1%High Priority

Maximum Subarray

Array Divide and Conquer Dynamic Programming

#61

Rank

#1171MediumFrequency: 80.9%High Priority

Shortest Path in Binary Matrix

#62

Rank

#277MediumFrequency: 80.7%High Priority

Find the Celebrity

Two Pointers Graph Theory Interactive

#63

Rank

#2691MediumFrequency: 80.7%High Priority

Count Vowel Strings in Ranges

Array String Prefix Sum

#64

Rank

#5MediumFrequency: 80.5%High Priority

Longest Palindromic Substring

Two Pointers String Dynamic Programming Manacher

#65

Rank

#1023MediumFrequency: 79.9%High Priority

Time Based Key-Value Store

Hash Table String Binary Search Design

#66

Rank

#1713MediumFrequency: 79.6%High Priority

Dot Product of Two Sparse Vectors

Array Hash Table Two Pointers Design Linear Algebra

#67

Rank

#2464MediumFrequency: 79.6%High Priority

Time Needed to Rearrange a Binary String

String Dynamic Programming Simulation

#68

Rank

#31MediumFrequency: 79%High Priority

Next Permutation

Array Two Pointers

#69

Rank

#20EasyFrequency: 79%High Priority

Valid Parentheses

String Stack Bracket Sequences

#70

Rank

#129MediumFrequency: 78.4%High Priority

Sum Root to Leaf Numbers

Tree Depth-First Search Binary Tree

#71

Rank

#4180MediumFrequency: 78.4%High Priority

Pythagorean Distance Nodes in a Tree

Tree Breadth-First Search

#72

Rank

#176MediumFrequency: 78.4%High Priority

Second Highest Salary

Database

#73

Rank

#15MediumFrequency: 78.3%High Priority

3Sum

#74

Rank

#778MediumFrequency: 78.3%High Priority

Reorganize String

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

#75

Rank

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Beginner-Friendly Interview Questions

Easy to medium difficulty problems perfect for interview preparation beginners.

Total Problems

Easy

Medium

Hard

87%

Avg Frequency

Most Common Topics

Companies Asking These Questions

Meta (25)Databricks (7)TikTok (6)PayPal (5)LinkedIn (5)Uber (5)

Problems in This Collection

#1EasyFrequency: 100%High Priority

Two Sum

Asked at Google

Array Hash Table

Rank

#1371MediumFrequency: 100%High Priority

Minimum Remove to Make Valid Parentheses

Hash Table Linked List Design Doubly-Linked List

Rank

#146MediumFrequency: 100%High Priority

LRU Cache

Asked at Apple

Rank

#2710MediumFrequency: 100%High Priority

Minimum Operations to Reduce an Integer to 0

Dynamic Programming Greedy Bit Manipulation

Rank

#286MediumFrequency: 100%High Priority

Walls and Gates

Rank

#1538MediumFrequency: 100%High Priority

Maximum Points You Can Obtain from Cards

Array Sliding Window Prefix Sum

Rank

#6MediumFrequency: 100%High Priority

Zigzag Conversion

String

Rank

#362MediumFrequency: 100%High Priority

Design Hit Counter

Array Binary Search Design Queue Data Stream

Rank

#752MediumFrequency: 97.6%High Priority

IP to CIDR

String Bit Manipulation

Rank

#200MediumFrequency: 97.3%High Priority

Number of Islands

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

#10

Rank

#408EasyFrequency: 96.8%High Priority

Valid Word Abbreviation

#11

Rank

#364MediumFrequency: 95.4%High Priority

Nested List Weight Sum II

Stack Depth-First Search Breadth-First Search

#12

Rank

#680EasyFrequency: 95.1%High Priority

Valid Palindrome II

Two Pointers String Greedy

#13

Rank

#1306EasyFrequency: 94.7%High Priority

Minimum Absolute Difference

Array Sorting

#14

Rank

#1549MediumFrequency: 94.4%High Priority

Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit

Array Queue Sliding Window Heap (Priority Queue)Ordered Set+1 more

#15

Rank

#348MediumFrequency: 93.6%High Priority

Design Tic-Tac-Toe

Array Hash Table Design Matrix Simulation

#16

Rank

#314MediumFrequency: 93.4%High Priority

Binary Tree Vertical Order Traversal

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

#17

Rank

#215MediumFrequency: 93.3%High Priority

Kth Largest Element in an Array

Array Divide and Conquer Sorting Heap (Priority Queue)Quickselect

#18

Rank

#3MediumFrequency: 92.8%High Priority

Longest Substring Without Repeating Characters

#19

Rank

#300MediumFrequency: 89.7%High Priority

Longest Increasing Subsequence

Array Binary Search Dynamic Programming Longest Increasing Subsequence

#20

Rank

#227MediumFrequency: 89.3%High Priority

Basic Calculator II

Math String Stack

#21

Rank

#1790MediumFrequency: 88.5%High Priority

Lowest Common Ancestor of a Binary Tree III

Hash Table Two Pointers Tree Binary Tree Binary Lifting+1 more

#22

Rank

#443MediumFrequency: 88.1%High Priority

String Compression

#23

Rank

#339MediumFrequency: 87.9%High Priority

Nested List Weight Sum

Depth-First Search Breadth-First Search

#24

Rank

#912MediumFrequency: 87.7%High Priority

Random Pick with Weight

Array Math Binary Search Prefix Sum Randomized

#25

Rank

#560MediumFrequency: 87.2%High Priority

Subarray Sum Equals K

Array Hash Table Prefix Sum

#26

Rank

#772MediumFrequency: 87%High Priority

Construct Quad Tree

Array Divide and Conquer Tree Matrix

#27

Rank

#543EasyFrequency: 86.8%High Priority

Diameter of Binary Tree

Tree Depth-First Search Binary Tree DP on Trees

#28

Rank

#694MediumFrequency: 86.6%High Priority

Number of Distinct Islands

Array Hash Table Depth-First Search Breadth-First Search Union-Find+3 more

#29

Rank

#236MediumFrequency: 86.4%High Priority

Lowest Common Ancestor of a Binary Tree

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

#30

Rank

#88EasyFrequency: 86.3%High Priority

Merge Sorted Array

#31

Rank

#210MediumFrequency: 85.9%High Priority

Course Schedule II

Depth-First Search Breadth-First Search Graph Theory Topological Sort

#32

Rank

#162MediumFrequency: 85.8%High Priority

Find Peak Element

Array Binary Search

#33

Rank

#1019EasyFrequency: 85.8%High Priority

Squares of a Sorted Array

#34

Rank

#251MediumFrequency: 85.6%High Priority

Flatten 2D Vector

Array Two Pointers Design Iterator

#35

Rank

#199MediumFrequency: 85.4%High Priority

Binary Tree Right Side View

Tree Depth-First Search Breadth-First Search Binary Tree

#36

Rank

#56MediumFrequency: 84.6%High Priority

Merge Intervals

Array Sorting Quicksort

#37

Rank

#438MediumFrequency: 84.4%High Priority

Find All Anagrams in a String

#38

Rank

#3876MediumFrequency: 84.3%High Priority

Transform Array to All Equal Elements

Array Greedy

#39

Rank

#50MediumFrequency: 84.1%High Priority

Pow(x, n)

Math Recursion

#40

Rank

#121EasyFrequency: 83.8%High Priority

Best Time to Buy and Sell Stock

#41

Rank

#253MediumFrequency: 83.8%High Priority

Meeting Rooms II

Array Two Pointers Greedy Sorting Heap (Priority Queue)+1 more

#42

Rank

#71MediumFrequency: 83.7%High Priority

Simplify Path

#43

Rank

#2217MediumFrequency: 83.7%High Priority

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

String Tree Depth-First Search Binary Tree Binary Lifting+1 more

#44

Rank

#198MediumFrequency: 83.7%High Priority

House Robber

#45

Rank

#1366MediumFrequency: 83.2%High Priority

First Unique Number

Array Hash Table Design Queue Data Stream

#46

Rank

#1046MediumFrequency: 83.2%High Priority

Max Consecutive Ones III

Array Binary Search Sliding Window Prefix Sum

#47

Rank

#1112EasyFrequency: 82.7%High Priority

Find Words That Can Be Formed by Characters

Array Hash Table String Counting

#48

Rank

#125EasyFrequency: 82.6%High Priority

Valid Palindrome

#49

Rank

#1909MediumFrequency: 82.6%High Priority

Buildings With an Ocean View

Array Stack Monotonic Stack

#50

Rank

#1397MediumFrequency: 82.5%High Priority

Search Suggestions System

Array String Binary Search Trie Sorting+1 more

#51

Rank

#1190MediumFrequency: 82.4%High Priority

Smallest Common Region

Array Hash Table String Tree Depth-First Search+3 more

#52

Rank

#207MediumFrequency: 82.3%High Priority

Course Schedule

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

#53

Rank

#230MediumFrequency: 82.3%High Priority

Kth Smallest Element in a BST

Tree Depth-First Search Binary Search Tree Binary Tree

#54

Rank

#244MediumFrequency: 82.3%High Priority

Shortest Word Distance II

Array Hash Table Two Pointers String Design

#55

Rank

#3231MediumFrequency: 82%High Priority

Minimum Number of Coins to be Added

Array Greedy Sorting

#56

Rank

#1036MediumFrequency: 82%High Priority

Rotting Oranges

Array Hash Table String Sorting

#57

Rank

#49MediumFrequency: 81.6%High Priority

Group Anagrams

Asked at Oracle

#58

Rank

#2MediumFrequency: 81.4%High Priority

Add Two Numbers

Linked List Math Recursion

#59

Rank

#347MediumFrequency: 81.3%High Priority

Top K Frequent Elements

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

#60

Rank

#53MediumFrequency: 81.1%High Priority

Maximum Subarray

Array Divide and Conquer Dynamic Programming

#61

Rank

#1171MediumFrequency: 80.9%High Priority

Shortest Path in Binary Matrix

#62

Rank

#277MediumFrequency: 80.7%High Priority

Find the Celebrity

Two Pointers Graph Theory Interactive

#63

Rank

#2691MediumFrequency: 80.7%High Priority

Count Vowel Strings in Ranges

Array String Prefix Sum

#64

Rank

#5MediumFrequency: 80.5%High Priority

Longest Palindromic Substring

Two Pointers String Dynamic Programming Manacher

#65

Rank

#1023MediumFrequency: 79.9%High Priority

Time Based Key-Value Store

Hash Table String Binary Search Design

#66

Rank

#1713MediumFrequency: 79.6%High Priority

Dot Product of Two Sparse Vectors

Array Hash Table Two Pointers Design Linear Algebra

#67

Rank

#2464MediumFrequency: 79.6%High Priority

Time Needed to Rearrange a Binary String

String Dynamic Programming Simulation

#68

Rank

#31MediumFrequency: 79%High Priority

Next Permutation

Array Two Pointers

#69

Rank

#20EasyFrequency: 79%High Priority

Valid Parentheses

String Stack Bracket Sequences

#70

Rank

#129MediumFrequency: 78.4%High Priority

Sum Root to Leaf Numbers

Tree Depth-First Search Binary Tree

#71

Rank

#4180MediumFrequency: 78.4%High Priority

Pythagorean Distance Nodes in a Tree

Tree Breadth-First Search

#72

Rank

#176MediumFrequency: 78.4%High Priority

Second Highest Salary

Database

#73

Rank

#15MediumFrequency: 78.3%High Priority

3Sum

#74

Rank

#778MediumFrequency: 78.3%High Priority

Reorganize String

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

#75

Rank

Other Collections

Most Frequent Interview Questions

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

Advanced Interview Problems

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