Hash Table Interview Questions

Rank

#3594MediumFrequency: 100%

Identify the Largest Outlier in an Array

Array Hash Table Counting Enumeration

Rank

#3638HardFrequency: 100%

Minimum Operations to Make Character Frequencies Equal

Hash Table String Dynamic Programming Counting Enumeration

Rank

#49MediumFrequency: 100%

Group Anagrams

Asked at Oracle

Array Hash Table String Sorting

Rank

#532MediumFrequency: 100%

K-diff Pairs in an Array

Array Hash Table Two Pointers Binary Search Sorting

Rank

#1423MediumFrequency: 100%

Maximum Number of Occurrences of a Substring

Rank

#146MediumFrequency: 100%

LRU Cache

Asked at Flipkart

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

#348MediumFrequency: 93%

Design Tic-Tac-Toe

Asked at Databricks

Array Hash Table Design Matrix Simulation

#10

Rank

#1790MediumFrequency: 91%

Lowest Common Ancestor of a Binary Tree III

Hash Table Two Pointers Tree Binary Tree

#11

Rank

#460HardFrequency: 88%

LFU Cache

#12

Rank

#621MediumFrequency: 85%

Task Scheduler

Array Hash Table Greedy Sorting Heap (Priority Queue)Counting

#13

Rank

#3MediumFrequency: 84%

Longest Substring Without Repeating Characters

#14

Rank

#560MediumFrequency: 81%

Subarray Sum Equals K

#15

Rank

#305HardFrequency: 79%

Number of Islands II

#16

Rank

#347MediumFrequency: 76%

Top K Frequent Elements

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

#17

Rank

#1713MediumFrequency: 76%

Dot Product of Two Sparse Vectors

Array Hash Table Two Pointers Design

#18

Rank

#1915EasyFrequency: 73%

Check if One String Swap Can Make Strings Equal

Asked at DoorDash

#19

Rank

#778MediumFrequency: 72%

Reorganize String

Hash Table String Greedy Sorting Heap (Priority Queue)Counting

#20

Rank

#3710HardFrequency: 72%

Design an Array Statistics Tracker

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

#21

Rank

#139MediumFrequency: 72%

Word Break

Array Hash Table String Dynamic Programming Trie Memoization

#22

Rank

#381HardFrequency: 72%

Insert Delete GetRandom O(1) - Duplicates allowed

Hash Table String Breadth-First Search

#23

Rank

#127HardFrequency: 71%

Word Ladder

Asked at Apple

#24

Rank

#1108MediumFrequency: 69%

Analyze User Website Visit Pattern

Array Hash Table Sorting

#25

Rank

#138MediumFrequency: 67%

Copy List with Random Pointer

Hash Table Linked List

#26

Rank

#893MediumFrequency: 64%

All Nodes Distance K in Binary Tree

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

#27

Rank

#244MediumFrequency: 63%

Shortest Word Distance II

Array Hash Table Two Pointers String Design

#28

Rank

#432HardFrequency: 63%

All O`one Data Structure

#29

Rank

#721MediumFrequency: 62%

Accounts Merge

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

#30

Rank

#694MediumFrequency: 62%

Number of Distinct Islands

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

#31

Rank

#76HardFrequency: 60%

Minimum Window Substring

#32

Rank

#133MediumFrequency: 60%

Clone Graph

Hash Table Depth-First Search Breadth-First Search Graph

#33

Rank

#807MediumFrequency: 60%

Custom Sort String

Hash Table String Sorting

#34

Rank

#1029HardFrequency: 60%

Vertical Order Traversal of a Binary Tree

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

#35

Rank

#17MediumFrequency: 56%

Letter Combinations of a Phone Number

#36

Rank

#12MediumFrequency: 55%

Integer to Roman

#37

Rank

#128MediumFrequency: 55%

Longest Consecutive Sequence

#38

Rank

#169EasyFrequency: 55%

Majority Element

Array Hash Table Divide and Conquer Sorting Counting

#39

Rank

#205EasyFrequency: 55%

Isomorphic Strings

Hash Table String

#40

Rank

#291MediumFrequency: 55%

Word Pattern II

#41

Rank

#567MediumFrequency: 55%

Permutation in String

Hash Table Two Pointers String Sliding Window

#42

Rank

#1147MediumFrequency: 55%

Flip Columns For Maximum Number of Equal Rows

#43

Rank

#1468EasyFrequency: 55%

Check If N and Its Double Exist

Array Hash Table Two Pointers Binary Search Sorting

#44

Rank

#141EasyFrequency: 53%

Linked List Cycle

Hash Table Linked List Two Pointers

#45

Rank

#2300MediumFrequency: 53%

Construct String With Repeat Limit

Hash Table String Greedy Heap (Priority Queue)Counting

#46

Rank

#380MediumFrequency: 51%

Insert Delete GetRandom O(1)

#47

Rank

#387EasyFrequency: 51%

First Unique Character in a String

Hash Table String Queue Counting

#48

Rank

#398MediumFrequency: 51%

Random Pick Index

Hash Table Math Reservoir Sampling Randomized

#49

Rank

#976MediumFrequency: 48%

Minimum Area Rectangle

Array Hash Table Math Geometry Sorting

#50

Rank

#126HardFrequency: 45%

Word Ladder II

Hash Table String Backtracking Breadth-First Search

#51

Rank

#1034HardFrequency: 45%

Subarrays with K Different Integers

Array Hash Table Sliding Window Counting

#52

Rank

#3410HardFrequency: 45%

Find Longest Self-Contained Substring

Hash Table String Binary Search Prefix Sum

#53

Rank

#249MediumFrequency: 43%

Group Shifted Strings

Array Hash Table String

#54

Rank

#325MediumFrequency: 43%

Maximum Size Subarray Sum Equals k

#55

Rank

#523MediumFrequency: 43%

Continuous Subarray Sum

Array Hash Table Math Prefix Sum

#56

Rank

#13EasyFrequency: 42%

Roman to Integer

#57

Rank

#268EasyFrequency: 42%

Missing Number

Array Hash Table Math Binary Search Bit Manipulation Sorting

#58

Rank

#359EasyFrequency: 42%

Logger Rate Limiter

Hash Table Design Data Stream

#59

Rank

#383EasyFrequency: 42%

Ransom Note

#60

Rank

#424MediumFrequency: 42%

Longest Repeating Character Replacement

#61

Rank

#1330MediumFrequency: 42%

Longest Arithmetic Subsequence of Given Difference

Array Hash Table Dynamic Programming

#62

Rank

#36MediumFrequency: 36%

Valid Sudoku

#63

Rank

#41HardFrequency: 33%

First Missing Positive

Start Free TrialNo credit card required View Pricing

#64

Rank

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Hash Table Interview Questions

Master 64 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

#3638HardFrequency: 100%

Minimum Operations to Make Character Frequencies Equal

Hash Table String Dynamic Programming Counting Enumeration

Rank

#49MediumFrequency: 100%

Group Anagrams

Asked at Oracle

Array Hash Table String Sorting

Rank

#532MediumFrequency: 100%

K-diff Pairs in an Array

Array Hash Table Two Pointers Binary Search Sorting

Rank

#1423MediumFrequency: 100%

Maximum Number of Occurrences of a Substring

Rank

#146MediumFrequency: 100%

LRU Cache

Asked at Flipkart

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

#348MediumFrequency: 93%

Design Tic-Tac-Toe

Asked at Databricks

Array Hash Table Design Matrix Simulation

#10

Rank

#1790MediumFrequency: 91%

Lowest Common Ancestor of a Binary Tree III

Hash Table Two Pointers Tree Binary Tree

#11

Rank

#460HardFrequency: 88%

LFU Cache

#12

Rank

#621MediumFrequency: 85%

Task Scheduler

Array Hash Table Greedy Sorting Heap (Priority Queue)Counting

#13

Rank

#3MediumFrequency: 84%

Longest Substring Without Repeating Characters

#14

Rank

#560MediumFrequency: 81%

Subarray Sum Equals K

#15

Rank

#305HardFrequency: 79%

Number of Islands II

#16

Rank

#347MediumFrequency: 76%

Top K Frequent Elements

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

#17

Rank

#1713MediumFrequency: 76%

Dot Product of Two Sparse Vectors

Array Hash Table Two Pointers Design

#18

Rank

#1915EasyFrequency: 73%

Check if One String Swap Can Make Strings Equal

Asked at DoorDash

#19

Rank

#778MediumFrequency: 72%

Reorganize String

Hash Table String Greedy Sorting Heap (Priority Queue)Counting

#20

Rank

#3710HardFrequency: 72%

Design an Array Statistics Tracker

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

#21

Rank

#139MediumFrequency: 72%

Word Break

Array Hash Table String Dynamic Programming Trie Memoization

#22

Rank

#381HardFrequency: 72%

Insert Delete GetRandom O(1) - Duplicates allowed

Hash Table String Breadth-First Search

#23

Rank

#127HardFrequency: 71%

Word Ladder

Asked at Apple

#24

Rank

#1108MediumFrequency: 69%

Analyze User Website Visit Pattern

Array Hash Table Sorting

#25

Rank

#138MediumFrequency: 67%

Copy List with Random Pointer

Hash Table Linked List

#26

Rank

#893MediumFrequency: 64%

All Nodes Distance K in Binary Tree

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

#27

Rank

#244MediumFrequency: 63%

Shortest Word Distance II

Array Hash Table Two Pointers String Design

#28

Rank

#432HardFrequency: 63%

All O`one Data Structure

#29

Rank

#721MediumFrequency: 62%

Accounts Merge

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

#30

Rank

#694MediumFrequency: 62%

Number of Distinct Islands

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

#31

Rank

#76HardFrequency: 60%

Minimum Window Substring

#32

Rank

#133MediumFrequency: 60%

Clone Graph

Hash Table Depth-First Search Breadth-First Search Graph

#33

Rank

#807MediumFrequency: 60%

Custom Sort String

Hash Table String Sorting

#34

Rank

#1029HardFrequency: 60%

Vertical Order Traversal of a Binary Tree

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

#35

Rank

#17MediumFrequency: 56%

Letter Combinations of a Phone Number

#36

Rank

#12MediumFrequency: 55%

Integer to Roman

#37

Rank

#128MediumFrequency: 55%

Longest Consecutive Sequence

#38

Rank

#169EasyFrequency: 55%

Majority Element

Array Hash Table Divide and Conquer Sorting Counting

#39

Rank

#205EasyFrequency: 55%

Isomorphic Strings

Hash Table String

#40

Rank

#291MediumFrequency: 55%

Word Pattern II

#41

Rank

#567MediumFrequency: 55%

Permutation in String

Hash Table Two Pointers String Sliding Window

#42

Rank

#1147MediumFrequency: 55%

Flip Columns For Maximum Number of Equal Rows

#43

Rank

#1468EasyFrequency: 55%

Check If N and Its Double Exist

Array Hash Table Two Pointers Binary Search Sorting

#44

Rank

#141EasyFrequency: 53%

Linked List Cycle

Hash Table Linked List Two Pointers

#45

Rank

#2300MediumFrequency: 53%

Construct String With Repeat Limit

Hash Table String Greedy Heap (Priority Queue)Counting

#46

Rank

#380MediumFrequency: 51%

Insert Delete GetRandom O(1)

#47

Rank

#387EasyFrequency: 51%

First Unique Character in a String

Hash Table String Queue Counting

#48

Rank

#398MediumFrequency: 51%

Random Pick Index

Hash Table Math Reservoir Sampling Randomized

#49

Rank

#976MediumFrequency: 48%

Minimum Area Rectangle

Array Hash Table Math Geometry Sorting

#50

Rank

#126HardFrequency: 45%

Word Ladder II

Hash Table String Backtracking Breadth-First Search

#51

Rank

#1034HardFrequency: 45%

Subarrays with K Different Integers

Array Hash Table Sliding Window Counting

#52

Rank

#3410HardFrequency: 45%

Find Longest Self-Contained Substring

Hash Table String Binary Search Prefix Sum

#53

Rank

#249MediumFrequency: 43%

Group Shifted Strings

Array Hash Table String

#54

Rank

#325MediumFrequency: 43%

Maximum Size Subarray Sum Equals k

#55

Rank

#523MediumFrequency: 43%

Continuous Subarray Sum

Array Hash Table Math Prefix Sum

#56

Rank

#13EasyFrequency: 42%

Roman to Integer

#57

Rank

#268EasyFrequency: 42%

Missing Number

Array Hash Table Math Binary Search Bit Manipulation Sorting

#58

Rank

#359EasyFrequency: 42%

Logger Rate Limiter

Hash Table Design Data Stream

#59

Rank

#383EasyFrequency: 42%

Ransom Note

#60

Rank

#424MediumFrequency: 42%

Longest Repeating Character Replacement

#61

Rank

#1330MediumFrequency: 42%

Longest Arithmetic Subsequence of Given Difference

Array Hash Table Dynamic Programming

#62

Rank

#36MediumFrequency: 36%

Valid Sudoku

#63

Rank

#41HardFrequency: 33%

First Missing Positive