Awesome

Leetcode solutions in Java

My accepted leetcode solutions to some of the common interview problems.

Array

Pascals Traiangle II (Easy)
Product Of Array Except Self (Medium)
Rotate Matrix (Medium)
Set Matrix Zeroes (Medium)
Third Maximum Number (Easy)
Two Sum (Easy)
TwoSum II (Easy)
Can Place Flowers (Easy)
Merge Intervals (Medium)
First Missing Positive (Hard)
Fruit Into Baskets (Medium)
MaxProduct Of Three Numbers (Easy)
Missing Number (Easy)
Merge Sorted Array (Easy)
Rotate Array (Easy)
Sort Colors (Medium)
Battleships in a Board (Medium)
Find the Celebrity (Medium)
Meeting Rooms (Easy)
Longest Continuous Increasing Subsequence (Easy)
Sparse Matrix Multiplication (Medium)
Read N Characters Given Read4 (Easy)
Maximum Swap (Medium)
H-Index (Medium)
Insert Interval (Hard)
Increasing Triplet Subsequence (Medium)
K Empty Slots (Hard)
Subarray Sum Equals K (Medium)
Pour Water (Medium)
Relative Ranks (Easy)
Next Greater Element I (Easy)
Largest Number At Least Twice of Others (Easy)
Minimum Moves to Equal Array Elements II (Median)
Image Smoother (Easy)
Minimum Index Sum of Two Lists (Easy)
Card Flipping Game (Medium)
Employee Free Time (Hard)
Best Meeting Point (Hard)
My Calendar III (Hard)
Champagne Tower (Medium)
Valid Tic-Tac-Toe State (Medium)
Number of Subarrays with Bounded Maximum (Medium)
Surface Area of 3D Shapes (Easy)
Max Consecutive Ones (Easy)
Max Consecutive Ones II (Medium)
Add to Array-Form of Integer (Easy)
Find Pivot Index (Easy)
Largest Time for Given Digits (Easy)
Minimum Time Difference (Medium)
Reveal Cards In Increasing Order (Medium)
Sort Array By Parity II (Easy)
Matrix Cells in Distance Order (Easy)
Maximum Sum of Two Non-Overlapping Subarrays (Medium)
Longest Line of Consecutive One in Matrix (Medium)
Array Partition I (Easy)
Relative Sort Array (Easy)
Meeting Scheduler (Medium)
Minimum Swaps to Group All 1's Together (Medium)
Array Nesting (Medium)

Backtracking

Binary Search

Minimum Sorted Rotated Array (Medium)
Search in a Rotated Sorted Array (Medium)
Search for a Range (Medium)
Sqrt(x) (Easy)
Search Insert Position (Easy)
Median of Two Sorted Arrays (Hard)
Pow(x, n) (Medium)
Find Peak Element (Medium)
Target Sum (Medium)
H-Index II (Medium)
Swim in Rising Water (Hard)
Time Based Key-Value Store (Medium)
Minimum Window Subsequence (Hard)
Koko Eating Bananas (Hard)
Single Element in a Sorted Array (Medium)

Bit Manipulation

Gray Code (Medium)
Hamming Distance (Easy)
Total Hamming Distance (Medium)
Divide Two Integers (Medium)
Binary Number with Alternating Bits (Easy)
Binary Watch (Easy)

Breadth First Search

Binaray Tree Level Order Traversal (Medium)
Word Ladder (Medium)
Word Ladder II (Hard)
Walls and Gates (Medium)
Open the lock (Medium)
Cut Off Trees for Golf Event (Hard)
Race Car (Hard)
Bus Routes (Hard)
Sliding Puzzle (Hard)
Matrix (Medium)
Rotting Oranges (Medium)

Depth First Search

Minesweeper (Medium)
Movie Recommend (Medium)
Number Of Islands (Medium)
Course Schedule (Medium)
Course Schedule II (Medium)
Alien Dictionary (Hard)
Graph Valid Tree (Medium)
Longest Consecutive Sequence (Hard)
Accounts Merge (Medium)
CloneGraph (Medium)
Island Perimeter (Easy)
Number of Distinct Islands (Medium)
Number of Distinct Islands II (Hard)
Smallest Rectangle Enclosing Black Pixels (Hard)
Bricks Falling When Hit (Hard)
Robot Room Cleaner (Hard)
Cracking the Safe (Hard)
All Paths From Source to Target (Medium)
Max Area of Island (Medium)
Satisfiability of Equality Equations (Medium)
Number of Enclaves (Medium)
As Far from Land as Possible (Medium)
Minimize Malware Spread (Hard)
Parallel Courses (Hard)
Connecting Cities With Minimum Cost (Medium)
Critical Connections in a Network (Hard)

Design

Copy List With Random Pointer (Medium)
Encode and Decode Tiny URL (Medium)
LFU Cache (Hard)
LRU Cache (Hard)
Insert Delete Get Random (Medium)
Serialize Deserialize Binary Tree (Hard)
Design Twitter (Medium)
Tic-Tac-Toe (Medium)
Implement Trie (Prefix Tree) (Medium)
Binary Search Tree Iterator (Medium)
Design Search Autocomplete System (Hard)
Design Excel Sum Formula (Hard)
Flatten Nested List Iterator (Medium)
Add and Search Word - Data structure design (Medium)
Prefix and Suffix Search (Hard)
Insert Delete GetRandom O(1) - Duplicates allowed (Hard)

Divide and Conquer

Dynamic Programming

Best Time To Buy and Sell Stocks (Easy)
Best Time to Buy and Sell Stock III (Hard)
Best Time to Buy and Sell Stock with Transaction Fee (Medium)
Climbing Stairs (Easy)
Coin Change (Medium)
Coin Change 2 (Medium)
Decode Ways (Medium)
House Robber (Easy)
House Robber II (Medium)
Longest Increasing Subsequence (Medium)
Longest Paliandromic Substring (Medium)
Longest Palindromic Subsequence (Medium)
Maximum Product Subarray (Medium)
Min Cost Climbing Stairs (Easy)
Palindrome Partitioning II (Hard)
UniqueBinary Search Trees (Medium)
Unique Binary Search Trees II (Medium)
WordBreak (Medium)
WordBreak II (Hard)
Concatenated Words (Hard)
Can I Win (Medium)
Maximum Subarray (Easy)
Dungeon Game (Hard)
2 Keys Keyboard (Medium)
Maximum Sum of 3 Non-Overlapping Subarrays (Hard)
Maximal Square (Medium)
Continuous Subarray Sum (Medium)
Decode Ways II (Hard)
Palindromic Substrings (Medium)
Number of Longest Increasing Subsequence (Medium)
Combination Sum IV (Medium)
Paint House II (Hard)
Split Array Largest Sum (Hard)
Number Of Corner Rectangles (Medium)
Burst Balloons (Hard)
Largest Plus Sign (Medium)
Palindrome Pairs (Hard)
Cherry Pickup (Hard)
Knight Probability in Chessboard (Medium)
Largest Sum of Averages (Medium)
Minimum Number of Refueling Stops (Hard)
Cat and Mouse (Hard)
Stone Game (Medium)
Odd Even Jump (Hard)
Profitable Schemes (Hard)
Maximum Vacation Days (Hard)
Russian Doll Envelopes (Hard)
Student Attendance Record II (Hard)
Out of Boundary Paths (Medium)
Remove Boxes (Hard)
Stickers to Spell Word (Hard)
Ones and Zeroes (Medium)
Encode String with Shortest Length (Hard)
Length of Longest Fibonacci Subsequence (Medium)
Make Array Strictly Increasing (Hard)
Minimum Number of Taps to Open to Water a Garden (Hard)
Delete Columns to Make Sorted III (Hard)
Handshakes That Don't Cross (Hard)
Minimum Difficulty of a Job Schedule (Hard)
Jump Game V (Hard)
Freedom Trail (Hard)
Strange Printer (Hard)
Minimum Cost to Merge Stones (Hard)
Interleaving String (Hard)
Count Vowels Permutation (Hard)
Non-negative Integers without Consecutive Ones (Hard)
Bomb Enemy (Medium)
Number of Dice Rolls With Target Sum (Medium)
Distinct Subsequences (Hard)
Distinct Subsequences II (Hard)
Minimum Distance to Type a Word Using Two Fingers (Hard)
Valid Palindrome III (Hard)
Palindrome Partitioning III (Hard)
Tiling a Rectangle with the Fewest Squares (Hard)
Longest Chunked Palindrome Decomposition (Hard)
Stone Game III (Hard)
Number of Ways to Stay in the Same Place After Some Steps (Hard)
Toss Strange Coins (Medium)
Knight Dialer (Medium)
Palindrome Removal (Hard)
Restore The Array (Hard)
Cherry Pickup II (Hard)
Constrained Subsequence Sum (Hard)
Largest Multiple of Three (Hard)
Largest Multiple of Three (Hard)
Number of Music Playlists (Hard)
Paint House III (Hard)
Shortest Path Visiting All Nodes (Hard)
Smallest Sufficient Team (Hard)
Stone Game IV (Hard)
Tallest Billboard (Hard)
Count Different Palindromic Subsequences (Hard)
Number of Paths with Max Score (Hard)

Greedy

Jump Game (Medium)
Jump Game II (Hard)
Course Schedule III (Medium)
GasStation (Medium)
Non-Overlapping Intervals (Medium)
Minimum Number of Arrows to Burst Balloons (Medium)
Queue Reconstruction By Height (Medium)
Task Scheduler (Medium)
Maximum Length of Pair Chain (Medium)
Lemonade Change (Easy)
Score After Flipping Matrix (Medium)
IPO (Hard)
String Without AAA or BBB (Medium)
Boats to Save People (Medium)
Broken Calculator (Medium)
Two City Scheduling (Easy)
Minimum Time to Build Blocks (Hard)
Reducing Dishes (Hard)

Hashing

Anagrams (Medium)
Group Anagrams (Medium)
Kdiff Pairs In a Array (Easy)
Sort Character by Frequency (Medium)
Two Sum (Easy)
Valid Anagram (Easy)
Maximum Size Subarray Sum Equals k (Medium)
Contiguous Array (Medium)
Brick Wall (Medium)
Partition Labels (Medium)
Custom Sort String (Medium)
Short Encoding of Words (Medium)
Substring with Concatenation of All Words (Hard)
Distribute Candies (Easy)
Groups of Special-Equivalent Strings (Easy)
Number of Atoms (Hard)
Analyze User Website Visit Pattern (Medium)
String Transforms Into Another String (Hard)

Heap

Sliding Window Maximum (Hard)
The Skyline Problem (Hard)
Meeting Rooms II (Medium)
Top K Frequent Words (Medium)
Candy (Hard)
Smallest Rotation with Highest Score (Hard)
Maximum Frequency Stack (Hard)
Reachable Nodes In Subdivided Graph (Hard)
K Closest Points to Origin (Medium)
Distant Barcodes (Medium)

Linked List

Intersection of two Linked-Lists (Easy)
Linked List Cycle (Easy)
Merge K Sorted Lists (Hard)
Merge Two Sorted List (Easy)
Paliandrome List (Easy)
Reverse Linked List (Easy)
Delete Node in a Linked List (Easy)
Reverse Nodes in k-Group (Hard)
Swap Nodes in Pairs (Medium)
Middle of Linked List (Easy)
Split Linked List in Parts (Medium)
Next Greater Node In Linked List (Medium)

Math

Add Two Numbers (Medium)
Count Primes (Easy)
Rotate Function (Medium)
Water and Jug Problem (Medium)
Add Digits (Easy)
Excel Sheet Column Title (Easy)
Roman to Integer (Easy)
Bulb Switcher II (Medium)
Global and Local Inversions (Medium)
Solve the Equation (Medium)
Couples Holding Hands (Hard)
Reaching Points (Hard)
Nth Magical Number (Hard)
Squirrel Simulation (Medium)
Projection Area of 3D Shapes (Easy)
Decoded String at Index (Medium)
Base 7 (Easy)
Smallest Range I (Easy)
Largest Component Size by Common Factor (Hard)
Super Washing Machines (Hard)
Rectangle Overlap (Easy)
Nth Digit (Easy)

Reservoir Sampling

Random Pick Index (Medium)

Stack

String

First Unique Character In a String (Easy)
Repeated Substring Pattern (Easy)
Reverse Words In a String (Medium)
ReverseWords II (Medium)
String to Integer (Medium)
Text Justification (Hard)
ZigZag Conversion (Medium)
Implement StrStr (Easy)
Excel Sheet Column Number (Easy)
Compare Version Numbers (Easy)
Valid Palindrome (Easy)
Simplify Path (Medium)
Permutation in String (Medium)
Add Binary (Easy)
Valid Palindrome II (Easy)
One Edit Distance (Medium)
Count and Say (Easy)
Multiply Strings (Medium)
Longest Word in Dictionary through Deleting (Medium)
Isomorphic Strings (Easy)
String Compression (Easy)
Longest Common Prefix (Easy)
Find the Closest Palindrome (Hard)
Monotone Increasing Digits (Medium)
Shortest Palindrome (Hard)
Valid Word Abbreviation (Easy)
Longest Palindrome (Easy)
Replace Words (Medium)
Rotate String (Easy)
Keyboard Row (Easy)
Student Attendance Record I (Easy)
Split Concatenated Strings (Medium)
Valid Word Square (Easy)
Reconstruct Original Digits from English (Medium)
Push Dominoes (Medium)
Validate IP Address (Medium)
Reverse String II (Easy)
Find Words That Can Be Formed by Characters (Easy)
Minimum Add to Make Parentheses Valid (Medium)

Tree

Binaray Tree Right Side View (Medium)
Binary Tree Maximum Path Sum (Hard)
Boundary of Binary Tree (Medium)
Convert sorted array to BST (Medium)
Lowest Common Ancestor of a Binary Tree (Medium)
Lowest Common Ancestor of a BST (Easy)
Most Frequent Subtree Sum (Medium)
Path Sum III (Easy)
Convert Postorder and Inorder traversal to Binary Tree (Medium)
Convert Preorder and Inorder traversal to Binary Tree (Medium)
Sorted Array to BST (Medium)
Valid Binary Search Tree (Medium)
Largest BST Subtree (Medium)
Closest Binary Search Tree Value (Easy)
Inorder Successor in BST (Medium)
Construct String From Binary Tree (Easy)
Flatten Binary Tree to Linked List (Medium)
Populating Next Right Pointers in Each Node (Medium)
Populating Next Right Pointers in Each Node II (Medium)
Subtree of Another Tree (Easy)
Binary Tree Zigzag Level Order Traversal (Medium)
Binary Tree Inorder Traversal (Medium)
Symmetric Tree (Easy)
Maximum Binary Tree (Medium)
Find Bottom Left Tree Value (Medium)
Diameter of Binary Tree (Easy)
Binary Tree Paths (Easy)
Sum of Left Leaves (Easy)
Two Sum IV - Input is a BST (Easy)
Average of Levels in Binary Tree (Easy)
Convert Binary Search Tree to Sorted Doubly Linked List (Easy)
Same Tree (Easy)
Binary Tree Longest Consecutive SequencefindMinDifference II (Medium)
Minimum Absolute Difference in BST (Medium)
Equal Tree Partition (Medium)
Split BST (Medium)
Closest Leaf in a Binary Tree (Medium)
Maximum Width of Binary Tree (Medium)
Recover Binary Search Tree (Hard)
Binary Tree Postorder Traversal (Hard)
Serialize and Deserialize N-ary Tree (Hard)
Convert BST to Greater Tree (Easy)
All Nodes Distance K in Binary Tree (Medium)
All Possible Full Binary Trees (Medium)
Flip Equivalent Binary Trees (Medium)
Construct Binary Tree from String (Medium)
Find Largest Value in Each Tree Row (Medium)
Find Bottom Left Tree Value (Medium)
Maximum Level Sum of a Binary Tree (Medium)
Leaf-Similar Trees (Easy)
Binary Tree Tilt (Easy)

Two Pointers

Four Sum (Medium)
Longest Substring Witout Repeats (Medium)
Three Sum (Medium)
Trapping Rain Water (Hard)
3Sum Closest (Medium)
Move Zeroes (Easy)
Remove Duplicates (Easy)
Remove Duplicates II (Medium)
Minimum Size Subarray Sum (Medium)
Minimum Window Substring (Hard)
Smallest Range (Hard)
Subarray Product Less Than K (Medium)
Number of Matching Subsequences (Medium)
Subarrays with K Different Integers (Hard)
Last Substring in Lexicographical Order (Hard)