The accepted Java solutions and explanations to the leetcode algorithm.
- Array
- Backtracking
- BFS
- Binary Search
- Bit Manipulation
- Design
- DFS
- Dynamic Programming
- Greedy
- Hash Table
- Heap
- LinkedList
- Math
- Queue
- Sort
- String
- Tree
- Trie
- Two Pointers
- Union Find
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 22 | Generate Parentheses | Java | Medium |
| 46 | Permuations | Java | Medium |
| 47 | Permutations II | Java | Medium |
| 51 | N Queues | Java | Hard |
| 52 | N Queues II | Java | Hard |
| 79 | Word Search | Java | Medium |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 102 | Binary Tree Level Order Traversal | Java | Medium |
| 103 | Binary Tree Zigzag Level Order Traversal | Java | Medium |
| 107 | Binary Tree Level Order Traversal II | Java | Easy |
| 111 | Minimum Depth of Binary Tree | Java | Easy |
| 130 | Surrounded Regions | Java | Medium |
| 133 | Clone Graph | Java | Medium |
| 199 | Binary Tree Right Side View | Java | Medium |
| 200 | Number of Islands | Java | Medium |
| 207 | Course Schedule | Java | Medium |
| 210 | Course Schedule II | Java | Medium |
| 261 | Graph Valid Tree (locked) | Java | Medium |
| 286 | Walls And Gates | Java | Medium |
| 317 | Shortest Distance From All Buildings | Java | Hard |
| 417 | Pacific Atlantic Water Flow | Java | Medium |
| 490 | The Maze | Java | Medium |
| 499 | The Maze III | Java | Hard |
| 505 | The Maze II | Java | Medium |
| 513 | Find Bottom Left Tree Value | Java | Medium |
| 515 | Find Largest Value in Each Tree Row | Java | Medium |
| 529 | Minesweeper | Java | Medium |
| 582 | Kill Process | Java | Medium |
| 690 | Employee Importance | Java | Easy |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 33 | Search in Rotated Sorted Array | Java | Medium |
| 34 | Search For A Range | Java | Medium |
| 35 | Search Insert Position | Java | Easy |
| 69 | Sqrt | Java | Easy |
| 74 | Search a 2D Matrix | Java | Medium |
| 81 | Search In Rotated Sorted ArrayII | Java | Medium |
| 153 | Find Minimum In Rotated Sorted Array | Java | Easy |
| 154 | Find Minimum In Rotated Sorted Array II | Java | Easy |
| 162 | Find Peak Element | Java | Easy |
| 240 | Search a 2D Matrix II | Java | Easy |
| 270 | Closest Binary Search Tree Value | Java | Easy |
| 278 | First Bad Version | Java | Easy |
| 367 | Valid Perfect Square | Java | Easy |
| 441 | Arranging Coins | Java | Easy |
| 475 | Heaters | Java | Easy |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 136 | Single Number | Java | Easy |
| 137 | Single Number II | Java | Medium |
| 190 | Reverse Bit | Java | Easy |
| 191 | Number of Bits | Java | Easy |
| 201 | Bitwise AND of Numbers Range | Java | Medium |
| 231 | Power of Two | Java | Easy |
| 260 | Single Number III | Java | Medium |
| 318 | Maximum Product of Word Lengths | Java | Medium |
| 338 | Counting Bits | Java | Medium |
| 342 | Power of Four | Java | Easy |
| 371 | Sum of Two Integers | Java | Easy |
| 389 | Find the Difference | Java | Easy |
| 397 | Integer Replacement | Java | Medium |
| 401 | Binary Watch | Java | Easy |
| 405 | Convert a Number to Hexadecimal | Java | Easy |
| 461 | Hamming Distance | Java | Easy |
| 476 | Number Complement | Java | Easy |
| 477 | Total Hamming Distance | Java | Medium |
| 693 | Binary Number with Alternating Bits | Java | Easy |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 146 | LRU | Java | Hard |
| 155 | Min Stack | Java | Easy |
| 170 | Two Sum III DataStructure Design | Java | Easy |
| 225 | Implement Stack Using Queues | Java | Easy |
| 232 | Implement Queue Using Stacks | Java | Easy |
| 244 | Shortest Word Distance I | Java | Medium |
| 281 | Zigzag Iterator | Java | Medium |
| 284 | Peeking Iterator | Java | Medium |
| 341 | Flatten Nested List Iterator | Java | Medium |
| 346 | Moving Average From Data Stream | Java | Easy |
| 355 | Design Twitter | Java | Medium |
| 359 | Logger Rate Limiter | Java | Easy |
| 380 | Insert Delete GetRandom | Java | Medium |
| 381 | Insert Delete GetRandom Duplicates Allowed | Java | Hard |
| 635 | Design Log Storage System | Java | Medium |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 122 | Best Time to Buy and Sell Stock II | Java | Easy |
| 134 | Gas Station | Java | Medium |
| 135 | Candy | Java | Hard |
| 169 | Majority Element | Java | Easy |
| 229 | Majority Element II | Java | Medium |
| 406 | Queue Reconstruction by Height | Java | Medium |
| 455 | Assign Cookies | Java | Easy |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 218 | The Skyline Problem | Java | Hard |
| 264 | Ugly Number II | Java | Medium |
| 295 | Find Median From Data Stream | Java | Hard |
| 347 | Top K Frequent Elements | Java | Medium |
| 373 | Find K Pairs With Smallest Sums | Java | Medium |
| 407 | Trapping RainWater II | Java | Hard |
| 451 | Sort Characters By Frequency | Java | Medium |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 2 | Add Two Numbers | Java | Medium |
| 19 | Remove Nth Node From End of List | Java | Medium |
| 21 | Merge Two Sorted Linked List | Java | Easy |
| 23 | Merge K Sorted Lists | Java | Hard |
| 24 | Swap Nodes in Pairs | Java | Medium |
| 61 | Rotate List | Java | Medium |
| 82 | Remove Duplicates from Sorted List II | Java | Medium |
| 83 | Remove Duplicates | Java | Easy |
| 86 | Partition List | Java | Medium |
| 92 | Reverse Linked List II | Java | Medium |
| 138 | Copy List with Random Pointer | Java | Medium |
| 141 | Linked List Cycle | Java | Easy |
| 142 | Linked List Cycle II | Java | Medium |
| 143 | Reorder List | Java | Medium |
| 147 | Insertion Sort List | Java | Medium |
| 160 | Intersection of Two Linked List | Java | Easy |
| 203 | Remove Linked List Elements | Java | Easy |
| 206 | Reverse Linked List | Java | Easy |
| 234 | Palindrome Linked List | Java | Easy |
| 237 | Delete Node in a Linked List | Java | Easy |
| 328 | Odd Even Linked List | Java | Medium |
| 445 | Add Two Numbers II | Java | Medium |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 9 | Palindrome Number | Java | Easy |
| 50 | Pow | Java | Medium |
| 168 | Excel Sheet Column Title | Java | Easy |
| 171 | Excel Sheet Column Number | Java | Easy |
| 172 | Factorial Trailing Zeroes | Java | Easy |
| 223 | Rectangle Area | Java | Medium |
| 233 | Number Of Digit One | Java | Hard |
| 258 | Add Digits | Java | Easy |
| 263 | Ugly Number | Java | Easy |
| 326 | Power Of Three | Java | Easy |
| 365 | Water And Jug Problem | Java | Medium |
| 396 | Rotate Function | Java | Medium |
| 400 | Nth Digit | Java | Easy |
| 415 | Add String | Java | Easy |
| 423 | Reconstruct Original Digits From English | Java | Medium |
| 453 | Minimum Moves To Equal Array Elements | Java | Easy |
| 462 | Minimum Moves To Equal Array Element II | Java | Medium |
| 469 | Convex Polygon | Java | Medium |
| 507 | Perfect Number | Java | Easy |
| 573 | Squirrel Simulation | Java | Medium |
| 592 | Fraction Addition And Subtraction | Java | Medium |
| 598 | Range Addition II | Java | Easy |
| 633 | Sum Of Square Numbers | Java | Easy |
| 728 | Self Dividing Numbers | Java | Easy |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 239 | Sliding Window Maximum | Java | Hard |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 56 | Merge Intervals | Java | Medium |
| 75 | Sort Colors | Java | Medium |
| 148 | Sort List | Java | Medium |
| 179 | Largest Number | Java | Medium |
| 274 | H Index | Java | Medium |
| 349 | Intersection of Two Arrays | Java | Easy |
| 350 | Intersection of Two Arrays II | Java | Easy |
| 524 | Longest Word in Dictionary through Deleting | Java | Medium |
| Quick Sort | Java | ||
| Merge Sort | Java |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 95 | Unique Binary Search Trees II | Java | Medium |
| 117 | Populating Next Right Pointers in Eac hNode II | Java | Medium |
| 222 | Count Complete Tree Node | Java | Medium |
| 654 | Maximum Binary Tree | Java | Medium |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 208 | Implement Trie Prefix Tree | Java | Medium |
| 211 | Add And Search Word Data Structure Design | Java | Medium |
| 212 | Word Search II | Java | Hard |
| 421 | Maximum XOR Of Two Numbers In An Array | Java | Medium |
| 648 | Replace Words | Java | Medium |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 3 | Longest Substring without Repeating Characters | Java | Medium |
| 11 | Container with Most Water | Java | Medium |
| 15 | 3Sum | Java | Medium |
| 16 | 3SumClosest | Java | Medium |
| 18 | 4Sum | Java | Medium |
| 26 | Remove Duplicates from Sorted Array | Java | Easy |
| 27 | Remove Elements | Java | Easy |
| 28 | Implement strStr | Java | Easy |
| 76 | Minimum Window Substring | Java | Hard |
| 80 | Remove Duplicates from Sorted Array II | Java | Medium |
| 88 | Merge Sorted Array | Java | Easy |
| 125 | Valid Palindrome | Java | Easy |
| 167 | Two Sum II Input Array Is Sorted | Java | Easy |
| 209 | Minimum Size Subarray Sum | Java | Medium |
| 287 | Find The Duplicate | Java | Medium |
| 345 | Reverse Vowels Of A String | Java | Easy |
| 524 | Longest Word In Dictionary Through Deleting | Java | Medium |
| 532 | Kdiff Pairs In An Array | Java | Easy |
| 567 | Permutation In String | Java | Medium |
| # | Title | Solution | Difficulty |
|---|---|---|---|
| 128 | Longest Consecutive Sequence | Java | Hard |
| 305 | Number of Islands II(locked) | Java | Hard |
| 323 | Number of Connected Components in an Undirected Graph(locked) | Java | Medium |
| 547 | Friend Circles | Java | Medium |
| 684 | Redundant Connection | Java | Medium |