Hash Table Interview Questions

Rank

#3594MediumFrequency: 100%

Identify the Largest Outlier in an Array

Array Hash Table Counting Enumeration

Rank

#817EasyFrequency: 100%

Design HashMap

Array Hash Table Linked List Design Hash Function

Rank

#694MediumFrequency: 98%

Number of Distinct Islands

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

Rank

#314MediumFrequency: 97%

Binary Tree Vertical Order Traversal

Hash Table Tree Depth-First Search Breadth-First Search Sorting Binary Tree

Rank

#833HardFrequency: 95%

Bus Routes

Array Hash Table Breadth-First Search

Rank

#1790MediumFrequency: 91%

Lowest Common Ancestor of a Binary Tree III

Hash Table Two Pointers Tree Binary Tree

Rank

#1423MediumFrequency: 91%

Maximum Number of Occurrences of a Substring

Rank

#146MediumFrequency: 88%

LRU Cache

Rank

#621MediumFrequency: 85%

Task Scheduler

Array Hash Table Greedy Sorting Heap (Priority Queue)Counting

#10

Rank

#3MediumFrequency: 84%

Longest Substring Without Repeating Characters

#11

Rank

#387EasyFrequency: 83%

First Unique Character in a String

Hash Table String Queue Counting

#12

Rank

#1330MediumFrequency: 83%

Longest Arithmetic Subsequence of Given Difference

Array Hash Table Dynamic Programming

#13

Rank

#1108MediumFrequency: 83%

Analyze User Website Visit Pattern

Array Hash Table Sorting

#14

Rank

#424MediumFrequency: 82%

Longest Repeating Character Replacement

#15

Rank

#398MediumFrequency: 82%

Random Pick Index

Hash Table Math Reservoir Sampling Randomized

#16

Rank

#141EasyFrequency: 82%

Linked List Cycle

Hash Table Linked List Two Pointers

#17

Rank

#432HardFrequency: 82%

All O`one Data Structure

#18

Rank

#560MediumFrequency: 81%

Subarray Sum Equals K

#19

Rank

#348MediumFrequency: 81%

Design Tic-Tac-Toe

Array Hash Table Design Matrix Simulation

#20

Rank

#305HardFrequency: 79%

Number of Islands II

#21

Rank

#380MediumFrequency: 79%

Insert Delete GetRandom O(1)

#22

Rank

#166MediumFrequency: 79%

Fraction to Recurring Decimal

Asked at Databricks

#23

Rank

#356MediumFrequency: 77%

Line Reflection

Array Hash Table Math

#24

Rank

#347MediumFrequency: 76%

Top K Frequent Elements

Array Hash Table Divide and Conquer Sorting Heap (Priority Queue)Bucket Sort Counting Quickselect

#25

Rank

#1713MediumFrequency: 76%

Dot Product of Two Sparse Vectors

Array Hash Table Two Pointers Design

#26

Rank

#249MediumFrequency: 76%

Group Shifted Strings

Array Hash Table String

#27

Rank

#41HardFrequency: 74%

First Missing Positive

#28

Rank

#49MediumFrequency: 72%

Group Anagrams

Array Hash Table String Sorting

#29

Rank

#778MediumFrequency: 72%

Reorganize String

Hash Table String Greedy Sorting Heap (Priority Queue)Counting

#30

Rank

#3710HardFrequency: 72%

Design an Array Statistics Tracker

Hash Table Binary Search Design Queue Heap (Priority Queue)Data Stream Ordered Set

#31

Rank

#381HardFrequency: 72%

Insert Delete GetRandom O(1) - Duplicates allowed

#32

Rank

#383EasyFrequency: 72%

Ransom Note

#33

Rank

#325MediumFrequency: 71%

Maximum Size Subarray Sum Equals k

#34

Rank

#2532EasyFrequency: 71%

Remove Letter To Equalize Frequency

#35

Rank

#753MediumFrequency: 69%

Open the Lock

Array Hash Table String Breadth-First Search

#36

Rank

#1029HardFrequency: 69%

Vertical Order Traversal of a Binary Tree

Hash Table Tree Depth-First Search Breadth-First Search Sorting Binary Tree

#37

Rank

#807MediumFrequency: 68%

Custom Sort String

#38

Rank

#138MediumFrequency: 67%

Copy List with Random Pointer

Hash Table Linked List

#39

Rank

#353MediumFrequency: 67%

Design Snake Game

Array Hash Table Design Queue Simulation

#40

Rank

#128MediumFrequency: 66%

Longest Consecutive Sequence

#41

Rank

#893MediumFrequency: 64%

All Nodes Distance K in Binary Tree

Hash Table Tree Depth-First Search Breadth-First Search Binary Tree

#42

Rank

#127HardFrequency: 64%

Word Ladder

Hash Table String Breadth-First Search

#43

Rank

#244MediumFrequency: 63%

Shortest Word Distance II

Array Hash Table Two Pointers String Design

#44

Rank

#2695MediumFrequency: 63%

Find Score of an Array After Marking All Elements

Array Hash Table Sorting Heap (Priority Queue)Simulation

#45

Rank

#12MediumFrequency: 63%

Integer to Roman

#46

Rank

#721MediumFrequency: 62%

Accounts Merge

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

#47

Rank

#460HardFrequency: 60%

LFU Cache

#48

Rank

#76HardFrequency: 60%

Minimum Window Substring

#49

Rank

#133MediumFrequency: 60%

Clone Graph

Hash Table Depth-First Search Breadth-First Search Graph

#50

Rank

#2300MediumFrequency: 59%

Construct String With Repeat Limit

Hash Table String Greedy Heap (Priority Queue)Counting

#51

Rank

#1468EasyFrequency: 58%

Check If N and Its Double Exist

Array Hash Table Two Pointers Binary Search Sorting

#52

Rank

#139MediumFrequency: 57%

Word Break

Array Hash Table String Dynamic Programming Trie Memoization

#53

Rank

#523MediumFrequency: 57%

Continuous Subarray Sum

Asked at TikTok

Array Hash Table Math Prefix Sum

#54

Rank

#1775EasyFrequency: 57%

Design an Ordered Stream

Array Hash Table Design Data Stream

#55

Rank

#17MediumFrequency: 56%

Letter Combinations of a Phone Number

#56

Rank

#169EasyFrequency: 55%

Majority Element

Array Hash Table Divide and Conquer Sorting Counting

#57

Rank

#205EasyFrequency: 55%

Isomorphic Strings

Hash Table String

#58

Rank

#291MediumFrequency: 55%

Word Pattern II

#59

Rank

#567MediumFrequency: 55%

Permutation in String

Hash Table Two Pointers String Sliding Window

#60

Rank

#1147MediumFrequency: 55%

Flip Columns For Maximum Number of Equal Rows

#61

Rank

#126HardFrequency: 52%

Word Ladder II

Hash Table String Backtracking Breadth-First Search

#62

Rank

#3410HardFrequency: 51%

Find Longest Self-Contained Substring

Hash Table String Binary Search Prefix Sum

#63

Rank

#359EasyFrequency: 51%

Logger Rate Limiter

Hash Table Design Data Stream

#64

Rank

#1034HardFrequency: 50%

Subarrays with K Different Integers

Array Hash Table Sliding Window Counting

#65

Rank

#976MediumFrequency: 48%

Minimum Area Rectangle

Array Hash Table Math Geometry Sorting

#66

Rank

#13EasyFrequency: 44%

Roman to Integer

#67

Rank

#268EasyFrequency: 42%

Missing Number

Array Hash Table Math Binary Search Bit Manipulation Sorting

#68

Rank

#532MediumFrequency: 40%

K-diff Pairs in an Array

Array Hash Table Two Pointers Binary Search Sorting

#69

Rank

#36MediumFrequency: 36%

Valid Sudoku

#70

Rank

#242EasyFrequency: 22%

Valid Anagram

#71

Rank

#2552MediumFrequency: 21%

Maximum Sum of Distinct Subarrays With Length K

Array Hash Table Sliding Window

#72

Rank

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Hash Table Interview Questions

Master 72 hash table problems frequently asked in technical interviews. These questions test your understanding of hash tableconcepts and are essential for coding interview success.

Total Problems

Easy

Medium

Hard

Two Sum

Rank

#3594MediumFrequency: 100%

Identify the Largest Outlier in an Array

Array Hash Table Counting Enumeration

Rank

#817EasyFrequency: 100%

Design HashMap

Array Hash Table Linked List Design Hash Function

Rank

#694MediumFrequency: 98%

Number of Distinct Islands

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

Rank

#314MediumFrequency: 97%

Binary Tree Vertical Order Traversal

Hash Table Tree Depth-First Search Breadth-First Search Sorting Binary Tree

Rank

#833HardFrequency: 95%

Bus Routes

Array Hash Table Breadth-First Search

Rank

#1790MediumFrequency: 91%

Lowest Common Ancestor of a Binary Tree III

Hash Table Two Pointers Tree Binary Tree

Rank

#1423MediumFrequency: 91%

Maximum Number of Occurrences of a Substring

Rank

#146MediumFrequency: 88%

LRU Cache

Rank

#621MediumFrequency: 85%

Task Scheduler

Array Hash Table Greedy Sorting Heap (Priority Queue)Counting

#10

Rank

#3MediumFrequency: 84%

Longest Substring Without Repeating Characters

#11

Rank

#387EasyFrequency: 83%

First Unique Character in a String

Hash Table String Queue Counting

#12

Rank

#1330MediumFrequency: 83%

Longest Arithmetic Subsequence of Given Difference

Array Hash Table Dynamic Programming

#13

Rank

#1108MediumFrequency: 83%

Analyze User Website Visit Pattern

Array Hash Table Sorting

#14

Rank

#424MediumFrequency: 82%

Longest Repeating Character Replacement

#15

Rank

#398MediumFrequency: 82%

Random Pick Index

Hash Table Math Reservoir Sampling Randomized

#16

Rank

#141EasyFrequency: 82%

Linked List Cycle

Hash Table Linked List Two Pointers

#17

Rank

#432HardFrequency: 82%

All O`one Data Structure

#18

Rank

#560MediumFrequency: 81%

Subarray Sum Equals K

#19

Rank

#348MediumFrequency: 81%

Design Tic-Tac-Toe

Array Hash Table Design Matrix Simulation

#20

Rank

#305HardFrequency: 79%

Number of Islands II

#21

Rank

#380MediumFrequency: 79%

Insert Delete GetRandom O(1)

#22

Rank

#166MediumFrequency: 79%

Fraction to Recurring Decimal

Asked at Databricks

#23

Rank

#356MediumFrequency: 77%

Line Reflection

Array Hash Table Math

#24

Rank

#347MediumFrequency: 76%

Top K Frequent Elements

Array Hash Table Divide and Conquer Sorting Heap (Priority Queue)Bucket Sort Counting Quickselect

#25

Rank

#1713MediumFrequency: 76%

Dot Product of Two Sparse Vectors

Array Hash Table Two Pointers Design

#26

Rank

#249MediumFrequency: 76%

Group Shifted Strings

Array Hash Table String

#27

Rank

#41HardFrequency: 74%

First Missing Positive

#28

Rank

#49MediumFrequency: 72%

Group Anagrams

Array Hash Table String Sorting

#29

Rank

#778MediumFrequency: 72%

Reorganize String

Hash Table String Greedy Sorting Heap (Priority Queue)Counting

#30

Rank

#3710HardFrequency: 72%

Design an Array Statistics Tracker

Hash Table Binary Search Design Queue Heap (Priority Queue)Data Stream Ordered Set

#31

Rank

#381HardFrequency: 72%

Insert Delete GetRandom O(1) - Duplicates allowed

#32

Rank

#383EasyFrequency: 72%

Ransom Note

#33

Rank

#325MediumFrequency: 71%

Maximum Size Subarray Sum Equals k

#34

Rank

#2532EasyFrequency: 71%

Remove Letter To Equalize Frequency

#35

Rank

#753MediumFrequency: 69%

Open the Lock

Array Hash Table String Breadth-First Search

#36

Rank

#1029HardFrequency: 69%

Vertical Order Traversal of a Binary Tree

Hash Table Tree Depth-First Search Breadth-First Search Sorting Binary Tree

#37

Rank

#807MediumFrequency: 68%

Custom Sort String

#38

Rank

#138MediumFrequency: 67%

Copy List with Random Pointer

Hash Table Linked List

#39

Rank

#353MediumFrequency: 67%

Design Snake Game

Array Hash Table Design Queue Simulation

#40

Rank

#128MediumFrequency: 66%

Longest Consecutive Sequence

#41

Rank

#893MediumFrequency: 64%

All Nodes Distance K in Binary Tree

Hash Table Tree Depth-First Search Breadth-First Search Binary Tree

#42

Rank

#127HardFrequency: 64%

Word Ladder

Hash Table String Breadth-First Search

#43

Rank

#244MediumFrequency: 63%

Shortest Word Distance II

Array Hash Table Two Pointers String Design

#44

Rank

#2695MediumFrequency: 63%

Find Score of an Array After Marking All Elements

Array Hash Table Sorting Heap (Priority Queue)Simulation

#45

Rank

#12MediumFrequency: 63%

Integer to Roman

#46

Rank

#721MediumFrequency: 62%

Accounts Merge

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

#47

Rank

#460HardFrequency: 60%

LFU Cache

#48

Rank

#76HardFrequency: 60%

Minimum Window Substring

#49

Rank

#133MediumFrequency: 60%

Clone Graph

Hash Table Depth-First Search Breadth-First Search Graph

#50

Rank

#2300MediumFrequency: 59%

Construct String With Repeat Limit

Hash Table String Greedy Heap (Priority Queue)Counting

#51

Rank

#1468EasyFrequency: 58%

Check If N and Its Double Exist

Array Hash Table Two Pointers Binary Search Sorting

#52

Rank

#139MediumFrequency: 57%

Word Break

Array Hash Table String Dynamic Programming Trie Memoization

#53

Rank

#523MediumFrequency: 57%

Continuous Subarray Sum

Asked at TikTok

Array Hash Table Math Prefix Sum

#54

Rank

#1775EasyFrequency: 57%

Design an Ordered Stream

Array Hash Table Design Data Stream

#55

Rank

#17MediumFrequency: 56%

Letter Combinations of a Phone Number

#56

Rank

#169EasyFrequency: 55%

Majority Element

Array Hash Table Divide and Conquer Sorting Counting

#57

Rank

#205EasyFrequency: 55%

Isomorphic Strings

Hash Table String

#58

Rank

#291MediumFrequency: 55%

Word Pattern II

#59

Rank

#567MediumFrequency: 55%

Permutation in String

Hash Table Two Pointers String Sliding Window

#60

Rank

#1147MediumFrequency: 55%

Flip Columns For Maximum Number of Equal Rows

#61

Rank

#126HardFrequency: 52%

Word Ladder II

Hash Table String Backtracking Breadth-First Search

#62

Rank

#3410HardFrequency: 51%

Find Longest Self-Contained Substring

Hash Table String Binary Search Prefix Sum

#63

Rank

#359EasyFrequency: 51%

Logger Rate Limiter

Hash Table Design Data Stream

#64

Rank

#1034HardFrequency: 50%

Subarrays with K Different Integers

Array Hash Table Sliding Window Counting

#65

Rank

#976MediumFrequency: 48%

Minimum Area Rectangle

Array Hash Table Math Geometry Sorting

#66

Rank

#13EasyFrequency: 44%

Roman to Integer

#67

Rank

#268EasyFrequency: 42%

Missing Number

Array Hash Table Math Binary Search Bit Manipulation Sorting

#68

Rank

#532MediumFrequency: 40%

K-diff Pairs in an Array

Array Hash Table Two Pointers Binary Search Sorting

#69

Rank

#36MediumFrequency: 36%

Valid Sudoku

#70

Rank

#242EasyFrequency: 22%

Valid Anagram

#71

Rank

#2552MediumFrequency: 21%

Maximum Sum of Distinct Subarrays With Length K