Most Frequent Interview Questions

String Stack

Rank

#146MediumFrequency: 100%High Priority

LRU Cache

Asked at Apple

Rank

#833HardFrequency: 100%High Priority

Bus Routes

Array Hash Table Breadth-First Search

Rank

#716HardFrequency: 100%High Priority

Max Stack

Linked List Stack Design Doubly-Linked List Ordered Set

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

Array Breadth-First Search Matrix

Rank

#68HardFrequency: 100%High Priority

Text Justification

Array String Simulation

Rank

#1538MediumFrequency: 100%High Priority

Maximum Points You Can Obtain from Cards

Array Sliding Window Prefix Sum

Rank

#750HardFrequency: 100%High Priority

Contain Virus

Array Depth-First Search Breadth-First Search Matrix Simulation

#10

Rank

#6MediumFrequency: 100%High Priority

Zigzag Conversion

String

#11

Rank

#362MediumFrequency: 100%High Priority

Design Hit Counter

Array Binary Search Design Queue Data Stream

#12

Rank

#752MediumFrequency: 97.6%High Priority

IP to CIDR

String Bit Manipulation

#13

Rank

#200MediumFrequency: 97.3%High Priority

Number of Islands

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

#14

Rank

#408EasyFrequency: 96.8%High Priority

Valid Word Abbreviation

#15

Rank

#364MediumFrequency: 95.4%High Priority

Nested List Weight Sum II

Stack Depth-First Search Breadth-First Search

#16

Rank

#269HardFrequency: 95.2%High Priority

Alien Dictionary

Array String Depth-First Search Breadth-First Search Graph Theory+2 more

#17

Rank

#680EasyFrequency: 95.1%High Priority

Valid Palindrome II

Two Pointers String Greedy

#18

Rank

#1306EasyFrequency: 94.7%High Priority

Minimum Absolute Difference

Array Sorting

#19

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

#20

Rank

#432HardFrequency: 93.8%High Priority

All O`one Data Structure

#21

Rank

#348MediumFrequency: 93.6%High Priority

Design Tic-Tac-Toe

Array Hash Table Design Matrix Simulation

#22

Rank

#314MediumFrequency: 93.4%High Priority

Binary Tree Vertical Order Traversal

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

#23

Rank

#215MediumFrequency: 93.3%High Priority

Kth Largest Element in an Array

Array Divide and Conquer Sorting Heap (Priority Queue)Quickselect

#24

Rank

#1352HardFrequency: 93%High Priority

Maximum Profit in Job Scheduling

Array Binary Search Dynamic Programming Sorting

#25

Rank

#3MediumFrequency: 92.8%High Priority

Longest Substring Without Repeating Characters

Asked at Infosys

#26

Rank

#329HardFrequency: 92.5%High Priority

Longest Increasing Path in a Matrix

Array Dynamic Programming Depth-First Search Breadth-First Search Graph Theory+4 more

#27

Rank

#124HardFrequency: 90.2%High Priority

Binary Tree Maximum Path Sum

Dynamic Programming Tree Depth-First Search Binary Tree DP on Trees

#28

Rank

#305HardFrequency: 89.9%High Priority

Number of Islands II

Array Hash Table Union-Find

#29

Rank

#300MediumFrequency: 89.7%High Priority

Longest Increasing Subsequence

Array Binary Search Dynamic Programming Longest Increasing Subsequence

#30

Rank

#227MediumFrequency: 89.3%High Priority

Basic Calculator II

Math String Stack

#31

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

#32

Rank

#443MediumFrequency: 88.1%High Priority

String Compression

Array Two Pointers Dynamic Programming Stack Monotonic Stack

#33

Rank

#42HardFrequency: 88%High Priority

Trapping Rain Water

Asked at Amazon

#34

Rank

#339MediumFrequency: 87.9%High Priority

Nested List Weight Sum

Depth-First Search Breadth-First Search

#35

Rank

#912MediumFrequency: 87.7%High Priority

Random Pick with Weight

Array Math Binary Search Prefix Sum Randomized

#36

Rank

#560MediumFrequency: 87.2%High Priority

Subarray Sum Equals K

Array Hash Table Prefix Sum

#37

Rank

#772MediumFrequency: 87%High Priority

Construct Quad Tree

Array Divide and Conquer Tree Matrix

#38

Rank

#543EasyFrequency: 86.8%High Priority

Diameter of Binary Tree

Tree Depth-First Search Binary Tree DP on Trees

#39

Rank

#694MediumFrequency: 86.6%High Priority

Number of Distinct Islands

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

#40

Rank

#236MediumFrequency: 86.4%High Priority

Lowest Common Ancestor of a Binary Tree

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

#41

Rank

#88EasyFrequency: 86.3%High Priority

Merge Sorted Array

#42

Rank

#210MediumFrequency: 85.9%High Priority

Course Schedule II

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

#43

Rank

#162MediumFrequency: 85.8%High Priority

Find Peak Element

Array Binary Search

#44

Rank

#1019EasyFrequency: 85.8%High Priority

Squares of a Sorted Array

#45

Rank

#251MediumFrequency: 85.6%High Priority

Flatten 2D Vector

Array Two Pointers Design Iterator

#46

Rank

#199MediumFrequency: 85.4%High Priority

Binary Tree Right Side View

Tree Depth-First Search Breadth-First Search Binary Tree

#47

Rank

#56MediumFrequency: 84.6%High Priority

Merge Intervals

Array Sorting Quicksort

#48

Rank

#438MediumFrequency: 84.4%High Priority

Find All Anagrams in a String

#49

Rank

#3876MediumFrequency: 84.3%High Priority

Transform Array to All Equal Elements

Array (28)Depth-First Search (13)Hash Table (12)Breadth-First Search (12)String (11)Two Pointers (8)Sorting (8)Matrix (7)

Array Greedy

#50

Rank

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Most Frequent Interview Questions

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

Total Problems

Easy

Medium

Hard

92%

Avg Frequency

Most Common Topics

Companies Asking These Questions

Meta (16)Uber (6)Databricks (4)TikTok (4)LinkedIn (3)DoorDash (3)

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

String Stack

Rank

#146MediumFrequency: 100%High Priority

LRU Cache

Asked at Apple

Rank

#833HardFrequency: 100%High Priority

Bus Routes

Array Hash Table Breadth-First Search

Rank

#716HardFrequency: 100%High Priority

Max Stack

Linked List Stack Design Doubly-Linked List Ordered Set

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

Array Breadth-First Search Matrix

Rank

#68HardFrequency: 100%High Priority

Text Justification

Array String Simulation

Rank

#1538MediumFrequency: 100%High Priority

Maximum Points You Can Obtain from Cards

Array Sliding Window Prefix Sum

Rank

#750HardFrequency: 100%High Priority

Contain Virus

Array Depth-First Search Breadth-First Search Matrix Simulation

#10

Rank

#6MediumFrequency: 100%High Priority

Zigzag Conversion

String

#11

Rank

#362MediumFrequency: 100%High Priority

Design Hit Counter

Array Binary Search Design Queue Data Stream

#12

Rank

#752MediumFrequency: 97.6%High Priority

IP to CIDR

String Bit Manipulation

#13

Rank

#200MediumFrequency: 97.3%High Priority

Number of Islands

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

#14

Rank

#408EasyFrequency: 96.8%High Priority

Valid Word Abbreviation

#15

Rank

#364MediumFrequency: 95.4%High Priority

Nested List Weight Sum II

Stack Depth-First Search Breadth-First Search

#16

Rank

#269HardFrequency: 95.2%High Priority

Alien Dictionary

Array String Depth-First Search Breadth-First Search Graph Theory+2 more

#17

Rank

#680EasyFrequency: 95.1%High Priority

Valid Palindrome II

Two Pointers String Greedy

#18

Rank

#1306EasyFrequency: 94.7%High Priority

Minimum Absolute Difference

Array Sorting

#19

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

#20

Rank

#432HardFrequency: 93.8%High Priority

All O`one Data Structure

#21

Rank

#348MediumFrequency: 93.6%High Priority

Design Tic-Tac-Toe

Array Hash Table Design Matrix Simulation

#22

Rank

#314MediumFrequency: 93.4%High Priority

Binary Tree Vertical Order Traversal

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

#23

Rank

#215MediumFrequency: 93.3%High Priority

Kth Largest Element in an Array

Array Divide and Conquer Sorting Heap (Priority Queue)Quickselect

#24

Rank

#1352HardFrequency: 93%High Priority

Maximum Profit in Job Scheduling

Array Binary Search Dynamic Programming Sorting

#25

Rank

#3MediumFrequency: 92.8%High Priority

Longest Substring Without Repeating Characters

Asked at Infosys

#26

Rank

#329HardFrequency: 92.5%High Priority

Longest Increasing Path in a Matrix

Array Dynamic Programming Depth-First Search Breadth-First Search Graph Theory+4 more

#27

Rank

#124HardFrequency: 90.2%High Priority

Binary Tree Maximum Path Sum

Dynamic Programming Tree Depth-First Search Binary Tree DP on Trees

#28

Rank

#305HardFrequency: 89.9%High Priority

Number of Islands II

Array Hash Table Union-Find

#29

Rank

#300MediumFrequency: 89.7%High Priority

Longest Increasing Subsequence

Array Binary Search Dynamic Programming Longest Increasing Subsequence

#30

Rank

#227MediumFrequency: 89.3%High Priority

Basic Calculator II

Math String Stack

#31

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

#32

Rank

#443MediumFrequency: 88.1%High Priority

String Compression

Array Two Pointers Dynamic Programming Stack Monotonic Stack

#33

Rank

#42HardFrequency: 88%High Priority

Trapping Rain Water

Asked at Amazon

#34

Rank

#339MediumFrequency: 87.9%High Priority

Nested List Weight Sum

Depth-First Search Breadth-First Search

#35

Rank

#912MediumFrequency: 87.7%High Priority

Random Pick with Weight

Array Math Binary Search Prefix Sum Randomized

#36

Rank

#560MediumFrequency: 87.2%High Priority

Subarray Sum Equals K

Array Hash Table Prefix Sum

#37

Rank

#772MediumFrequency: 87%High Priority

Construct Quad Tree

Array Divide and Conquer Tree Matrix

#38

Rank

#543EasyFrequency: 86.8%High Priority

Diameter of Binary Tree

Tree Depth-First Search Binary Tree DP on Trees

#39

Rank

#694MediumFrequency: 86.6%High Priority

Number of Distinct Islands

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

#40

Rank

#236MediumFrequency: 86.4%High Priority

Lowest Common Ancestor of a Binary Tree

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

#41

Rank

#88EasyFrequency: 86.3%High Priority

Merge Sorted Array

#42

Rank

#210MediumFrequency: 85.9%High Priority

Course Schedule II

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

#43

Rank

#162MediumFrequency: 85.8%High Priority

Find Peak Element

Array Binary Search

#44

Rank

#1019EasyFrequency: 85.8%High Priority

Squares of a Sorted Array

#45

Rank

#251MediumFrequency: 85.6%High Priority

Flatten 2D Vector

Array Two Pointers Design Iterator

#46

Rank

#199MediumFrequency: 85.4%High Priority

Binary Tree Right Side View

Tree Depth-First Search Breadth-First Search Binary Tree

#47

Rank

#56MediumFrequency: 84.6%High Priority

Merge Intervals

Array Sorting Quicksort

#48

Rank

#438MediumFrequency: 84.4%High Priority

Find All Anagrams in a String

#49

Rank

#3876MediumFrequency: 84.3%High Priority

Transform Array to All Equal Elements