#1Easy

Contains Duplicate

Arrays & Hashing

#2Easy

Valid Anagram

Arrays & Hashing

#3Easy

Two Sum

Arrays & Hashing

#4Medium

Group Anagrams

Arrays & Hashing

#5Medium

Top K Frequent Elements

Arrays & Hashing

#6Medium

Product of Array Except Self

Arrays & Hashing

#7Medium

Valid Sudoku

Arrays & Hashing

#8Medium

Encode and Decode Strings

Arrays & Hashing

#9Medium

Longest Consecutive Sequence

Arrays & Hashing

#10Easy

Valid Palindrome

Two Pointers

#11Medium

Two Sum II - Input Array Is Sorted

Two Pointers

#12Medium

3Sum

Two Pointers

#13Medium

Container With Most Water

Two Pointers

#14Hard

Trapping Rain Water

Two Pointers

#15Easy

Best Time to Buy and Sell Stock

Sliding Window

#16Medium

Longest Substring Without Repeating Characters

Sliding Window

#17Medium

Longest Repeating Character Replacement

Sliding Window

#18Medium

Permutation in String

Sliding Window

#19Hard

Minimum Window Substring

Sliding Window

#20Hard

Sliding Window Maximum

Sliding Window

#21Easy

Valid Parentheses

Stack

#22Medium

Min Stack

Stack

#23Medium

Evaluate Reverse Polish Notation

Stack

#24Medium

Generate Parentheses

Stack

#25Medium

Daily Temperatures

Stack

#26Medium

Car Fleet

Stack

#27Hard

Largest Rectangle in Histogram

Stack

#28Easy

Binary Search

Binary Search

#29Medium

Search a 2D Matrix

Binary Search

#30Medium

Koko Eating Bananas

Binary Search

#31Medium

Find Minimum in Rotated Sorted Array

Binary Search

#32Medium

Search in Rotated Sorted Array

Binary Search

#33Medium

Time Based Key-Value Store

Binary Search

#34Hard

Median of Two Sorted Arrays

Binary Search

#35Easy

Reverse Linked List

Linked List

#36Easy

Merge Two Sorted Lists

Linked List

#37Medium

Reorder List

Linked List

#38Medium

Remove Nth Node From End of List

Linked List

#39Medium

Copy List with Random Pointer

Linked List

#40Medium

Add Two Numbers

Linked List

#41Easy

Linked List Cycle

Linked List

#42Medium

Find the Duplicate Number

Linked List

#43Medium

LRU Cache

Linked List

#44Hard

Merge k Sorted Lists

Linked List

#45Hard

Reverse Nodes in k-Group

Linked List

#46Easy

Invert Binary Tree

Trees

#47Easy

Maximum Depth of Binary Tree

Trees

#48Easy

Diameter of Binary Tree

Trees

#49Easy

Balanced Binary Tree

Trees

#50Easy

Same Tree

Trees

#51Easy

Subtree of Another Tree

Trees

#52Medium

Lowest Common Ancestor of a Binary Search Tree

Trees

#53Medium

Binary Tree Level Order Traversal

Trees

#54Medium

Binary Tree Right Side View

Trees

#55Medium

Count Good Nodes in Binary Tree

Trees

#56Medium

Validate Binary Search Tree

Trees

#57Medium

Kth Smallest Element in a BST

Trees

#58Medium

Construct Binary Tree from Preorder and Inorder Traversal

Trees

#59Hard

Binary Tree Maximum Path Sum

Trees

#60Hard

Serialize and Deserialize Binary Tree

Trees

#61Medium

Implement Trie (Prefix Tree)

Tries

#62Medium

Design Add and Search Words Data Structure

Tries

#63Hard

Word Search II

Tries

#64Easy

Kth Largest Element in a Stream

Heap / Priority Queue

#65Easy

Last Stone Weight

Heap / Priority Queue

#66Medium

K Closest Points to Origin

Heap / Priority Queue

#67Medium

Kth Largest Element in an Array

Heap / Priority Queue

#68Medium

Task Scheduler

Heap / Priority Queue

#69Medium

Design Twitter

Heap / Priority Queue

#70Hard

Find Median from Data Stream

Heap / Priority Queue

#71Medium

Subsets

Backtracking

#72Medium

Combination Sum

Backtracking

#73Medium

Permutations

Backtracking

#74Medium

Subsets II

Backtracking

#75Medium

Combination Sum II

Backtracking

#76Medium

Word Search

Backtracking

#77Medium

Palindrome Partitioning

Backtracking

#78Medium

Letter Combinations of a Phone Number

Backtracking

#79Hard

N-Queens

Backtracking

#80Medium

Number of Islands

Graphs

#81Medium

Clone Graph

Graphs

#82Medium

Max Area of Island

Graphs

#83Medium

Pacific Atlantic Water Flow

Graphs

#84Medium

Surrounded Regions

Graphs

#85Medium

Rotting Oranges

Graphs

#86Medium

Walls and Gates

Graphs

#87Medium

Course Schedule

Graphs

#88Medium

Course Schedule II

Graphs

#89Medium

Redundant Connection

Graphs

#90Medium

Number of Connected Components in an Undirected Graph

Graphs

#91Medium

Graph Valid Tree

Graphs

#92Hard

Word Ladder

Graphs

#93Hard

Reconstruct Itinerary

Advanced Graphs

#94Medium

Min Cost to Connect All Points

Advanced Graphs

#95Medium

Network Delay Time

Advanced Graphs

#96Hard

Swim in Rising Water

Advanced Graphs

#97Hard

Alien Dictionary

Advanced Graphs

#98Medium

Cheapest Flights Within K Stops

Advanced Graphs

#99Easy

Climbing Stairs

1-D DP

#100Easy

Min Cost Climbing Stairs

1-D DP

#101Medium

House Robber

1-D DP

#102Medium

House Robber II

1-D DP

#103Medium

Longest Palindromic Substring

1-D DP

#104Medium

Palindromic Substrings

1-D DP

#105Medium

Decode Ways

1-D DP

#106Medium

Coin Change

1-D DP

#107Medium

Maximum Product Subarray

1-D DP

#108Medium

Word Break

1-D DP

#109Medium

Longest Increasing Subsequence

1-D DP

#110Medium

Partition Equal Subset Sum

1-D DP

#111Medium

Unique Paths

2-D DP

#112Medium

Longest Common Subsequence

2-D DP

#113Medium

Best Time to Buy and Sell Stock with Cooldown

2-D DP

#114Medium

Coin Change II

2-D DP

#115Medium

Target Sum

2-D DP

#116Medium

Interleaving String

2-D DP

#117Hard

Longest Increasing Path in a Matrix

2-D DP

#118Hard

Distinct Subsequences

2-D DP

#119Medium

Edit Distance

2-D DP

#120Hard

Burst Balloons

2-D DP

#121Hard

Regular Expression Matching

2-D DP

#122Medium

Maximum Subarray

Greedy

#123Medium

Jump Game

Greedy

#124Medium

Jump Game II

Greedy

#125Medium

Gas Station

Greedy

#126Medium

Hand of Straights

Greedy

#127Medium

Merge Triplets to Form Target Triplet

Greedy

#128Medium

Partition Labels

Greedy

#129Medium

Valid Parenthesis String

Greedy

#130Medium

Insert Interval

Intervals

#131Medium

Merge Intervals

Intervals

#132Medium

Non-overlapping Intervals

Intervals

#133Easy

Meeting Rooms

Intervals

#134Medium

Meeting Rooms II

Intervals

#135Hard

Minimum Interval to Include Each Query

Intervals

#136Medium

Rotate Image

Math & Geometry

#137Medium

Spiral Matrix

Math & Geometry

#138Medium

Set Matrix Zeroes

Math & Geometry

#139Easy

Happy Number

Math & Geometry

#140Easy

Plus One

Math & Geometry

#141Medium

Pow(x, n)

Math & Geometry

#142Medium

Multiply Strings

Math & Geometry

#143Medium

Detect Squares

Math & Geometry

#144Easy

Single Number

Bit Manipulation

#145Easy

Number of 1 Bits

Bit Manipulation

#146Easy

Counting Bits

Bit Manipulation

#147Easy

Reverse Bits

Bit Manipulation

#148Easy

Missing Number

Bit Manipulation

#149Medium

Sum of Two Integers

Bit Manipulation

#150Medium

Reverse Integer

Bit Manipulation