Question Category Difficulty
132 Pattern Stack Medium
3Sum Array Medium
3Sum Closest Array Medium
4Sum Greedy Medium
4Sum II Hash Medium
A data structure with insert/remove/random in O(1) Design Medium
Add and Search Word - Data structure design Backtracking Medium
Add Binary Math Easy
Add Digits Math Easy
Add Strings Math Easy
Add Two Numbers Math Easy
Add Two Numbers II Linklist Medium
Additive Number Math Medium
All O`one Data Structure Design Hard
Anagrams Hash Medium
Arithmetic Slices Dynamic Programming Medium
Arithmetic Slices II - Subsequence Dynamic Programming Hard
Arranging Coins Search Easy
Assign Cookies Greedy Easy
Balanced Binary Tree Tree Medium
Basic Calculator Stack Hard
Basic Calculator II String Medium
Battleships in a Board Math Medium
Best Time to Buy and Sell Stock Dynamic Programming Easy
Best Time to Buy and Sell Stock II Greedy Medium
Best Time to Buy and Sell Stock III Dynamic Programming Hard
Best Time to Buy and Sell Stock IV Dynamic Programming Hard
Best Time to Buy and Sell Stock with Cooldown Dynamic Programming Medium
Binary Search Tree Iterator Tree Medium
Binary Tree Inorder Traversal Tree Medium
Binary Tree Level Order Traversal Tree Medium
Binary Tree Level Order Traversal II Tree Medium
Binary Tree Maximum Path Sum Tree Hard
Binary Tree Paths Tree Easy
Binary Tree Post Order Traversal Tree Medium
Binary Tree Preorder Traversal Tree Medium
Binary Tree Right Side View Tree Medium
Binary Tree Zigzag Level Order Traversal Tree Medium
Binary Watch Backtracking Easy
Bitwise AND of Numbers Range Bit Manipulation Medium
Bubble Sort Sort Easy
Build Stack by Queue Stack Easy
Bulb Switcher Math Medium
Bulls and Cows Hash Easy
Burst Balloons Dynamic Programming Hard
Calculate Diameter of Binary Tree Tree Medium
Calculate Diameter of Multi-Node Tree Tree Hard
Calculate String Formula Result Stack Hard
Can I Win Dynamic Programming Medium
Candy Hash Hard
Check Rotated String String Easy
Climbing Stairs Dynamic Programming Easy
Clone Graph Graph Medium
Coin Change Dynamic Programming Medium
Combination Sum Backtracking Medium
Combination Sum II Backtracking Medium
Combination Sum III Backtracking Medium
Combination Sum IV Dynamic Programming Medium
Combinations Backtracking Medium
Compare Version Numbers String Easy
Concatenated Words Dynamic Programming Hard
Construct Binary Tree from Inorder and Postorder Traversal Tree Medium
Construct Binary Tree from Preorder and Inorder Traversal Dynamic Programming Easy
Container With Most Water Math Medium
Contains Duplicate Hash Easy
Contains Duplicate II Hash Easy
Contains Duplicate III Tree Medium
Convert a Number to Hexadecimal Bit Manipulation Easy
Convert Sorted Array to Binary Search Tree Tree Medium
Convert Sorted List to Binary Search Tree Tree Medium
Copy List with Random Pointer Greedy Hard
Count and Say String Easy
Count Complete Tree Nodes Tree Medium
Count Numbers with Unique Digits Dynamic Programming Medium
Count of Range Sum Tree Hard
Count of Smaller Numbers After Self Math Hard
Count Primes Math Easy
Count The Repetitions Dynamic Programming Hard
Counting Bits Recursion Medium
Course Schedule Graph Medium
Course Schedule II Graph Medium
Create Maximum Number Greedy Hard
Data Stream as Disjoint Intervals Tree Hard
Decode String Recursion Medium
Decode Ways Dynamic Programming Medium
Delete Node in a BST Tree Medium
Delete Node in a Linked List Linklist Easy
Design Twitter Design Medium
Different Ways to Add Parentheses Recursion Medium
Distinct Subsequences Dynamic Programming Hard
Divide Two Integers Math Medium
Edit Distance Dynamic Programming Hard
Elimination Game Array Medium
Evaluate Division Graph Medium
Evaluate Reverse Polish Notation Stack Medium
Excel Sheet Column Number Math Easy
Excel Sheet Column Title Math Easy
Expression Add Operators Recursion Medium
Factorial Trailing Zeroes Math Easy
Find All Anagrams in a String Hash Easy
Find All Duplicates in an Array Array Medium
Find All Numbers Disappeared in an Array Array Easy
Find K Pairs with Smallest Sums Array Medium
Find Median from Data Stream Design Medium
Find Median Number in Unsorted Array Sort Medium
Find Minimum in Rotated Sorted Array Search Medium
Find Minimum in Rotated Sorted Array II Search Medium
Find Peak Element Search Medium
Find Right Interval Search Medium
Find the Difference Hash Easy
Find the Duplicate Number Math Hard
First Bad Version Binary Search Easy
First Missing Positive Array Hard
First Unique Character in a String String Easy
Fizz Buzz String Easy
Flatten Binary Tree to Linked List Tree Medium
Flatten Nested List Iterator Linklist Medium
Fraction to Recurring Decimal Hash Medium
Frog Jump Dynamic Programming Hard
Game of Life Array Medium
Gas Station Hash Medium
Generate Parentheses Backtracking Medium
Gray Code Backtracking Medium
Group Anagrams Hash Medium
Guess Number Higher or Lower Binary Search Easy
Guess Number Higher or Lower II Dynamic Programming Medium
H-Index Hash Medium
H-Index II Binary Search Medium
Hamming Distance Bit Manipulation Easy
Happy Number Math Easy
Heaters Binary Search Easy
House Robber Dynamic Programming Easy
House Robber II Dynamic Programming Medium
House Robber III Dynamic Programming Medium
Huge Array Integer Search Search Easy
Implement Queue using Stacks Stack Easy
Implement Stack using Queues Stack Easy
Implement strStr() String Easy
Implement Trie (Prefix Tree) Tree Medium
Increasing Triplet Subsequence Array Medium
Insert Delete GetRandom O(1) Hash Hard
Insert Delete GetRandom O(1) - Duplicates allowed Hash Hard
Insert Interval Sort Hard
Insertion Sort List Linklist Medium
Integer Break Math Medium
Integer Replacemen Math Medium
Integer to English Words Math Hard
Integer To Roman Math Medium
Interleaving String String Hard
Intersection of Two Arrays Sort Easy
Intersection of Two Arrays II Array Easy
Intersection of Two Linked Lists Linklist Easy
Invert Binary Tree Tree Easy
Inverted Index Partitioning Design Medium
Is Subsequence Greedy Medium
Island Perimeter Hash Easy
Isomorphic Strings Hash Easy
Jump Game Hash Medium
Jump Game II Hash Hard
K-th Smallest in Lexicographical Order Search Hard
Kth Largest Element in an Array Heap Medium
Kth Smallest Element in a BST Tree Medium
Kth Smallest Element in a Sorted Matrix Binary Search Medium
Largest Divisible Subset Dynamic Programming Medium
Largest Number Math Medium
Largest Rectangle in Histogram Array Hard
Length of Last Word String Easy
Letter Combinations of a Phone Number Backtracking Medium
Lexicographical Numbers String Medium
Linked List Cycle Linklist Medium
Linked List Cycle II Linklist Medium
Linked List Random Node Linklist Medium
Longest Absolute File Path Array Medium
Longest Common Prefix String Easy
Longest Consecutive Sequence Array Hard
Longest Increasing Path in a Matrix Matrix Hard
Longest Increasing Subsequence Array Medium
Longest Palindrome Hash Easy
Longest Palindromic Substring String Medium
Longest Repeating Character Replacement Search Medium
Longest Substring with At Least K Repeating Characters Hash Medium
Longest Substring Without Repeating Characters String Medium
Longest Valid Parentheses Dynamic Programming Hard
Lowest Common Ancestor of a Binary Search Tree Tree Easy
Lowest Common Ancestor of a Binary Tree Tree Medium
LRU Cache Design Hard
Majority Element Array Easy
Majority Element II Array Medium
Matchsticks to Square Recursion Medium
Max Points on a Line Greedy Hard
Max Sum of Rectangle No Larger Than K Dynamic Programming Hard
Maximal Rectangle Dynamic Programming Hard
Maximal Square Dynamic Programming Medium
Maximum Depth of Binary Tree Tree Easy
Maximum Gap Sort Hard
Maximum Product of Word Lengths Bit Manipulation Medium
Maximum Product Subarray Dynamic Programming Medium
Maximum Subarray Array Medium
Maximum XOR of Two Numbers in an Array Bit Manipulation Medium
Median of Two Sorted Arrays Array Hard
Merge Intervals Sort Hard
Merge k Sorted Lists Linklist Hard
Merge Sorted Array Array Easy
Merge Two Sorted Lists Linklist Easy
Min Stack Stack Easy
Mini Parser String Medium
Minimum Depth of Binary Tree Tree Medium
Minimum Height Trees Tree Medium
Minimum Moves to Equal Array Elements Math Easy
Minimum Moves to Equal Array Elements II Math Medium
Minimum Number of Arrows to Burst Balloons Greedy Medium
Minimum Path Sum Dynamic Programming Medium
Minimum Size Subarray Sum Array Medium
Minimum Window Substring String Hard
Missing Number Bit Manipulation Medium
Move Zeroes Array Easy
Multiply Strings String Medium
N-Queens Backtracking Hard
N-Queens II Backtracking Hard
Next Permutation Array Medium
Nim Game Math Easy
Non-overlapping Intervals Greedy Medium
Nth Digit Math Easy
Number of 1 Bits Bit Manipulation Easy
Number of Boomerangs Hash Easy
Number of Digit One Math Hard
Number of Islands Graph Medium
Number of Segments in a String String Easy
Odd Even Linked List Linklist Medium
Ones and Zeroes Dynamic Programming Medium
Pacific Atlantic Water Flow Search Medium
Palindrome Linked List Linklist Easy
Palindrome Number Math Easy
Palindrome Pairs String Hard
Palindrome Partitioning Backtracking Medium
Palindrome Partitioning II Dynamic Programming Hard
Partition Equal Subset Sum Dynamic Programming Medium
Partition List Linklist Medium
Pascal's Triangle Array Easy
Pascal's Triangle II Array Easy
Patching Array Greedy Hard
Path Sum Tree Easy
Path Sum II Dynamic Programming Easy
Path Sum III Tree Easy
Peeking Iterator Iterrator Medium
Perfect Rectangle Matrix Hard
Perfect Squares Dynamic Programming Medium
Permutation Sequence Backtracking Medium
Permutations Backtracking Medium
Permutations II Backtracking Medium
Plus One Array Easy
Populating Next Right Pointers in Each Node Tree Medium
Populating Next Right Pointers in Each Node II Tree Hard
Pow Math Easy
Power of Four Math Easy
Power of Three Math Easy
Power of Two Math Easy
Product of Array Except Self Array Medium
Queue Reconstruction by Height Greedy Medium
Quick Sort Sort Medium
Random Pick Index Math Medium
Range Sum Query - Immutable Array Easy
Range Sum Query - Mutable Array Medium
Range Sum Query 2D - Immutable Matrix Medium
Ransom Note String Easy
Reconstruct Itinerary Graph Medium
Reconstruct Original Digits from English Math Medium
Recover Binary Search Tree Tree Medium
Rectangle Area Math Easy
Regular Expression Matching String Hard
Remove Duplicate Letters Greedy Hard
Remove Duplicates from Sorted Array Array Easy
Remove Duplicates from Sorted Array II Array Medium
Remove Duplicates from Sorted List Linklist Easy
Remove Duplicates from Sorted List II Linklist Medium
Remove Element Array Easy
Remove Invalid Parentheses Recursion Hard
Remove K Digits Stack Medium
Remove Linked List Elements Linklist Easy
Remove Nth Node From End of List Linklist Medium
Reorder List Linklist Medium
Repeated DNA Sequences Hash Medium
Repeated Substring Pattern String Easy
Restore IP Addresses Backtracking Medium
Reverse Bits Bit Manipulation Easy
Reverse Integer Math Easy
Reverse Linked List Linklist Easy
Reverse Linked List II Linklist Medium
Reverse Nodes in k-Group Backtracking Hard
Reverse String String Easy
Reverse Vowels of a String Hash Easy
Reverse Words in a String String Medium
Roman to Integer Math Easy
Rotate Array Array Easy
Rotate Function Math Easy
Rotate Image Array Medium
Rotate List Linklist Medium
Russian Doll Envelopes Array Hard
Same Tree Tree Easy
Scramble String Dynamic Programming Hard
Search a 2D Matrix Search Hard
Search a 2D Matrix II Binary Search Medium
Search for a Range Search Medium
Search in Rotated Sorted Array Search Hard
Search in Rotated Sorted Array II Search Medium
Search Insert Position Search Medium
Searching a 2D Sorted Matrix Part II Search Medium
Self Crossing Math Hard
Serialize and Deserialize Binary Tree Tree Hard
Serialize and Deserialize BST Tree Medium
Set Matrix Zeroes Array Medium
Shortest Palindrome String Hard
Shuffle an Array Array Medium
Simplify Path Stack Medium
Single Number Bit Manipulation Medium
Single Number II Bit Manipulation Medium
Single Number III Bit Manipulation Medium
Sliding Window Maximum Heap Hard
Sort Characters By Frequency Hash Medium
Sort Colors Sort Medium
Sort List Linklist Medium
Spiral Matrix Array Medium
Spiral Matrix II Array Medium
Split Array Largest Sum Dynamic Programming Hard
Sqrt(x) Math Medium
String to Integer String Medium
Strong Password Checker String Hard
Subsets Backtracking Medium
Subsets II Backtracking Medium
Substring with Concatenation of All Words String Hard
Sudoku Solver Backtracking Hard
Sum of Left Leaves Tree Easy
Sum of Two Integers Math Easy
Sum Root to Leaf Numbers Tree Medium
Summary Ranges Array Medium
Super Pow Math Medium
Super Ugly Number Math Medium
Surrounded Regions Search Medium
Swap Nodes in Pairs Linklist Medium
Symmetric Tree Tree Medium
Text Justification String Hard
The Skyline Problem Tree Hard
Third Maximum Number Array Easy
Top K Frequent Elements Hash Medium
Total Hamming Distance Bit Manipulation Medium
Trapping Rain Water Array Hard
Trapping Rain Water II Search Hard
Triangle Dynamic Programming Medium
Two Sum Greedy Easy
Two Sum II - Input array is sorted Array Medium
Ugly Number Math Easy
Ugly Number II Math Medium
Unique Binary Search Trees Tree Medium
Unique Binary Search Trees II Tree Medium
Unique Paths Dynamic Programming Medium
Unique Paths II Dynamic Programming Medium
Unique Substrings in Wraparound String Dynamic Programming Medium
UTF-8 Validation String Medium
Valid Anagram Sort Easy
Valid Number Math Hard
Valid Palindrome String Easy
Valid Parentheses Stack Easy
Valid Perfect Square Math Medium
Valid Sudoku Greedy Easy
Validate Binary Search Tree Tree Medium
Validate IP Address Dynamic Programming Medium
Verify Preorder Serialization of a Binary Tree Tree Medium
Water and Jug Problem Math Medium
What are Private key and public key - usage and purpose knowledge Easy
Wiggle Sort II Sort Medium
Wiggle Subsequence Dynamic Programming Medium
Wildcard Matching Dynamic Programming Hard
wood cut Search Medium
Word Break Dynamic Programming Medium
Word Break II Dynamic Programming Hard
Word Ladder String Medium
Word Ladder II String Hard
Word Pattern Hash Easy
Word Search Search Medium
Word Search II Backtracking Hard
ZigZag Conversion String Easy