System Design Interview Prep

Coding problems that help build system design thinking and scalability concepts.

60

Total Problems

6

Easy

39

Medium

15

Hard

80%

Avg Frequency

Most Common Topics

Array (31)Hash Table (30)Depth-First Search (17)Heap (Priority Queue) (15)Sorting (15)String (14)Tree (14)Binary Tree (13)

Companies Asking These Questions

Meta (18)Amazon (7)Uber (7)LinkedIn (7)DoorDash (5)Salesforce (3)

Problems in This Collection

#1EasyFrequency: 100%High Priority

Two Sum

Asked at Google

Array Hash Table

#1

Rank

#3594MediumFrequency: 100%High Priority

Identify the Largest Outlier in an Array

Asked at Amazon

Array Hash Table Counting Enumeration

#2

Rank

#3655MediumFrequency: 100%High Priority

Digit Operations to Make Two Integers Equal

Asked at Microsoft

Math Graph Heap (Priority Queue)Number Theory Shortest Path

#3

Rank

#3638HardFrequency: 100%High Priority

Minimum Operations to Make Character Frequencies Equal

Asked at TikTok

Hash Table String Dynamic Programming Counting Enumeration

#4

Rank

#3613MediumFrequency: 100%High Priority

Maximize Amount After Two Days of Conversions

Array String Depth-First Search Breadth-First Search Graph

#5

Rank

#716HardFrequency: 100%High Priority

Max Stack

Asked at LinkedIn

Linked List Stack Design Doubly-Linked List Ordered Set

#6

Rank

#49MediumFrequency: 100%High Priority

Group Anagrams

Asked at Oracle

Array Hash Table String Sorting

#7

Rank

#532MediumFrequency: 100%High Priority

K-diff Pairs in an Array

Asked at Salesforce

Array Hash Table Two Pointers Binary Search Sorting

#8

Rank

#1423MediumFrequency: 100%High Priority

Maximum Number of Occurrences of a Substring

Asked at Salesforce

Hash Table String Sliding Window

#9

Rank

#146MediumFrequency: 100%High Priority

LRU Cache

Asked at Flipkart

Hash Table Linked List Design Doubly-Linked List

#10

Rank

#295HardFrequency: 100%High Priority

Find Median from Data Stream

Asked at PayPal

Two Pointers Design Sorting Heap (Priority Queue)Data Stream

#11

Rank

#362MediumFrequency: 100%High Priority

Design Hit Counter

Asked at Databricks

Array Binary Search Design Queue Data Stream

#12

Rank

#314MediumFrequency: 97%High Priority

Binary Tree Vertical Order Traversal

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

#13

Rank

#658MediumFrequency: 96%High Priority

Find K Closest Elements

Asked at DoorDash

Array Two Pointers Binary Search Sliding Window Sorting+1 more

#14

Rank

#833HardFrequency: 95%High Priority

Bus Routes

Array Hash Table Breadth-First Search

#15

Rank

#348MediumFrequency: 93%High Priority

Design Tic-Tac-Toe

Asked at Databricks

Array Hash Table Design Matrix Simulation

#16

Rank

#215MediumFrequency: 92%High Priority

Kth Largest Element in an Array

Array Divide and Conquer Sorting Heap (Priority Queue)Quickselect

#17

Rank

#1790MediumFrequency: 91%High Priority

Lowest Common Ancestor of a Binary Tree III

Hash Table Two Pointers Tree Binary Tree

#18

Rank

#460HardFrequency: 88%High Priority

LFU Cache

Asked at Salesforce

Hash Table Linked List Design Doubly-Linked List

#19

Rank

#1478MediumFrequency: 87%High Priority

Maximum Number of Events That Can Be Attended

Asked at Oracle

Array Greedy Sorting Heap (Priority Queue)

#20

Rank

#621MediumFrequency: 85%High Priority

Task Scheduler

Asked at Amazon

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

#21

Rank

#3MediumFrequency: 84%High Priority

Longest Substring Without Repeating Characters

Asked at Microsoft

Hash Table String Sliding Window

#22

Rank

#366MediumFrequency: 84%High Priority

Find Leaves of Binary Tree

Asked at LinkedIn

Tree Depth-First Search Binary Tree

#23

Rank

#124HardFrequency: 83%High Priority

Binary Tree Maximum Path Sum

Asked at DoorDash

Dynamic Programming Tree Depth-First Search Binary Tree

#24

Rank

#560MediumFrequency: 81%High Priority

Subarray Sum Equals K

Array Hash Table Prefix Sum

#25

Rank

#236MediumFrequency: 79%High Priority

Lowest Common Ancestor of a Binary Tree

Tree Depth-First Search Binary Tree

#26

Rank

#269HardFrequency: 79%High Priority

Alien Dictionary

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

#27

Rank

#305HardFrequency: 79%High Priority

Number of Islands II

Array Hash Table Union Find

#28

Rank

#199MediumFrequency: 76%High Priority

Binary Tree Right Side View

Tree Depth-First Search Breadth-First Search Binary Tree

#29

Rank

#347MediumFrequency: 76%High Priority

Top K Frequent Elements

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

#30

Rank

#1713MediumFrequency: 76%High Priority

Dot Product of Two Sparse Vectors

Array Hash Table Two Pointers Design

#31

Rank

#543EasyFrequency: 74%High Priority

Diameter of Binary Tree

Tree Depth-First Search Binary Tree

#32

Rank

#975EasyFrequency: 73%High Priority

Range Sum of BST

Tree Depth-First Search Binary Search Tree Binary Tree

#33

Rank

#329HardFrequency: 73%High Priority

Longest Increasing Path in a Matrix

Asked at DoorDash

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

#34

Rank

#1397MediumFrequency: 73%High Priority

Search Suggestions System

Asked at DoorDash

Array String Binary Search Trie Sorting+1 more

#35

Rank

#1915EasyFrequency: 73%High Priority

Check if One String Swap Can Make Strings Equal

Asked at DoorDash

Hash Table String Counting

#36

Rank

#778MediumFrequency: 72%High Priority

Reorganize String

Asked at Amazon

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

#37

Rank

#3710HardFrequency: 72%High Priority

Design an Array Statistics Tracker

Asked at Amazon

Hash Table Binary Search Design Queue Heap (Priority Queue)+2 more

#38

Rank

#23HardFrequency: 72%High Priority

Merge k Sorted Lists

Linked List Divide and Conquer Heap (Priority Queue)Merge Sort

#39

Rank

#139MediumFrequency: 72%High Priority

Word Break

Asked at TikTok

Array Hash Table String Dynamic Programming Trie+1 more

#40

Rank

#235MediumFrequency: 72%High Priority

Lowest Common Ancestor of a Binary Search Tree

Asked at LinkedIn

Tree Depth-First Search Binary Search Tree Binary Tree

#41

Rank

#277MediumFrequency: 72%High Priority

Find the Celebrity

Asked at LinkedIn

Two Pointers Graph Interactive

#42

Rank

#381HardFrequency: 72%High Priority

Insert Delete GetRandom O(1) - Duplicates allowed

Asked at LinkedIn

Array Hash Table Math Design Randomized

#43

Rank

#127HardFrequency: 71%High Priority

Word Ladder

Hash Table String Breadth-First Search

#44

Rank

#1108MediumFrequency: 69%High Priority

Analyze User Website Visit Pattern

Asked at Amazon

Array Hash Table Sorting

#45

Rank

#129MediumFrequency: 68%High Priority

Sum Root to Leaf Numbers

Tree Depth-First Search Binary Tree

#46

Rank

#1014MediumFrequency: 68%High Priority

K Closest Points to Origin

Array Math Divide and Conquer Geometry Sorting+2 more

#47

Rank

#3647MediumFrequency: 67%High Priority

Zero Array Transformation III

Asked at Google

Array Greedy Sorting Heap (Priority Queue)Prefix Sum

#48

Rank

#138MediumFrequency: 67%High Priority

Copy List with Random Pointer

Asked at Amazon

Hash Table Linked List

#49

Rank

#2267HardFrequency: 64%High Priority

Minimum Difference in Sums After Removal of Elements

Asked at Amazon

Array Dynamic Programming Heap (Priority Queue)

#50

Rank

#758MediumFrequency: 64%High Priority

Convert Binary Search Tree to Sorted Doubly Linked List

Linked List Stack Tree Depth-First Search Binary Search Tree+2 more

#51

Rank

#893MediumFrequency: 64%High Priority

All Nodes Distance K in Binary Tree

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

#52

Rank

#399MediumFrequency: 63%High Priority

Evaluate Division

Array String Depth-First Search Breadth-First Search Union Find+2 more

#53

Rank

#772MediumFrequency: 63%High Priority

Construct Quad Tree

Array Divide and Conquer Tree Matrix

#54

Rank

#1549MediumFrequency: 63%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

#55

Rank

#244MediumFrequency: 63%High Priority

Shortest Word Distance II

Asked at LinkedIn

Array Hash Table Two Pointers String Design

#56

Rank

#432HardFrequency: 63%High Priority

All O`one Data Structure

Asked at LinkedIn

Hash Table Linked List Design Doubly-Linked List

#57

Rank

#270EasyFrequency: 62%High Priority

Closest Binary Search Tree Value

Binary Search Tree Depth-First Search Binary Search Tree Binary Tree

#58

Rank

#346EasyFrequency: 62%High Priority

Moving Average from Data Stream

Array Design Queue Data Stream

#59

Rank

#721MediumFrequency: 62%High Priority

Accounts Merge

Array Hash Table String Depth-First Search Breadth-First Search+2 more

#60

Rank

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