LeetCode solutions
Introduction
Solutions 1 - 50
1Two Sum – Medium
2 Add Two Numbers – Medium
3 Longest Substring Without Repeating Characters
4 Median of Two Sorted Arrays
5 Longest Palindromic Substring
6 ZigZag Conversion – Easy
7 Reverse Integer – Easy
8 String to Integer (atoi) – Easy
9 Palindrome Number – Easy
10 Regular Expression Matching
11 Container With Most Water – Medium
12 Integer to Roman – Medium
13 Roman to Integer – Easy
14 Longest Common Prefix – Easy
15 3Sum – Medium
16 3Sum Closest – Medium
17 Letter Combinations of a Phone Number – Medium
18 4Sum – Medium
19 Remove Nth Node From End of List – Easy
20 Valid Parentheses – Easy
21 Merge Two Sorted Lists – Easy
22 Generate Parentheses – Medium
23 Merge k Sorted Lists
24 Swap Nodes in Pairs – Medium
25 Reverse Nodes in k-Group
26 Remove Duplicates from Sorted Array – Easy
27 Remove Element – Easy
28 Implement strStr() – Easy
29 Divide Two Integers – Medium
31 Next Permutation – Medium
33 Search in Rotated Sorted Array – Hard
34 Search for a Range – Medium
35 Search Insert Position – Medium
36 Valid Sudoku – Easy
37 Sudoku Solver
38 Count and Say – Easy
39 Combination Sum – Medium
40 Combination Sum II – Medium
42 Trapping Rain Water
43 Multiply Strings – Medium
44 Wildcard Matching
46 Permutations – Medium
47 Permutations II – Medium
48 Rotate Image – Medium
49 Group Anagrams – Medium
50 Pow(x, n) – Medium
Solutions 51 - 100
53 Maximum Subarray – Medium
54 Spiral Matrix – Medium
55 Jump Game – Medium
56 Merge Intervals
57 Insert Interval
58 Length of Last Word – Easy
59 Spiral Matrix II – Medium
60 Permutation Sequence – Medium
61 Rotate List – Medium
62 Unique Paths – Medium
63 Unique Paths II – Medium
64 Minimum Path Sum – Medium
65 Valid Number
66 Plus One – Easy
67 Add Binary – Easy
68 Text Justification
69 Sqrt(x) – Medium
70 Climbing Stairs – Easy
71 Simplify Path – Medium
73 Set Matrix Zeroes – Medium
74 Search a 2D Matrix – Medium
75 Sort Colors – Medium
76 Minimum Window Substring
77 Combinations – Medium
78 Subsets – Medium
79 Word Search – Medium
80 Remove Duplicates from Sorted Array II – Medium
81 Search in Rotated Sorted Array II
82 Remove Duplicates from Sorted List II – Medium
83 Remove Duplicates from Sorted List – Easy
85 Maximal Rectangle
86 Partition List – Medium
88 Merge Sorted Array
89 Gray Code – Medium
90 Subsets II – Medium
91 Decode Ways – Medium
92 Reverse Linked List II – Medium
93 Restore IP Addresses – Medium
94 Binary Tree Inorder Traversal – Medium
95 Unique Binary Search Trees II – Medium
98 Validate Binary Search Tree
Solutions 101 - 150
101 Symmetric Tree – Easy
102 Binary Tree Level Order Traversal – Easy
103 Binary Tree Zigzag Level Order Traversal
104 Maximum Depth of Binary Tree – Easy
105 Construct Binary Tree from Preorder and Inorder Traversal – Medium
106 Construct Binary Tree from Inorder and Postorder Traversal – Medium
107 Binary Tree Level Order Traversal II – Easy
108 Convert Sorted Array to Binary Search Tree – Medium
109 Convert Sorted List to Binary Search Tree – Medium
110 Balanced Binary Tree – Easy
111Minimum Depth of Binary Tree – Easy
112 Path Sum – Easy
113 Path Sum II – Medium
114 Flatten Binary Tree to Linked List – Medium
116 Populating Next Right Pointers in Each Node – Medium
117 Populating Next Right Pointers in Each Node II
118 Pascal’s Triangle – Easy
119 Pascal’s Triangle II – Medium
120 Triangle – Medium
121 Best Time to Buy and Sell Stock – Medium
122 Best Time to Buy and Sell Stock II – Medium
123 Best Time to Buy and Sell Stock III – Hard
125 Valid Palindrome – Easy
127 Word Ladder – Medium
128 Longest Consecutive Sequence
129 Sum Root to Leaf Numbers – Medium
130 Surrounded Regions – Medium
131 Palindrome Partitioning – Medium
132 Palindrome Partitioning II – Hard
133 Clone Graph – Medium
134 Gas Station – Medium
136 Single Number – Medium
137 Single Number II – Medium
138 Copy List with Random Pointer
139 Word Break – Medium
140 Word Break II – Hard
141 Linked List Cycle – Medium
142 Linked List Cycle II – Medium
143 Reorder List – Medium
144 Binary Tree Preorder Traversal – Medium
145 Binary Tree Postorder Traversal – Hard
146 LRU Cache – Hard
147 Insertion Sort List – Medium
148 Sort List
149 Max Points on a Line
150 Evaluate Reverse Polish Notation – Medium
Solutions 151 - 200
151 Reverse Words in a String – Medium
152 Maximum Product Subarray – Medium
153 Find Minimum in Rotated Sorted Array – Medium
155 Min Stack – Easy
156 Binary Tree Upside Down – Medium
157 Read N Characters Given Read4 – Easy
158 Read N Characters Given Read4 II – Call multiple times Add to List QuestionEditorial Solution – Hard
159 Longest Substring with At Most Two Distinct Characters
160 Intersection of Two Linked Lists – Easy
161 One Edit Distance – Medium
162 Find Peak Element – Medium
163 Missing Ranges
165 Compare Version Numbers
166 Fraction to Recurring Decimal
167 Two Sum II – Input array is sorted – Medium
168 Excel Sheet Column Title – Easy
169 Majority Element – Easy
170 Two Sum III – Data structure design – Easy
171 Excel Sheet Column Number – Easy
172 Factorial Trailing Zeroes – Easy
173 Binary Search Tree Iterator – Medium
179 Largest Number – Medium
186 Reverse Words in a String II – Medium
187 Repeated DNA Sequences – Medium
189 Rotate Array – Easy
190 Java: Reverse Bits – Easy
191 Number of 1 Bits – Easy
198 House Robber – Easy
199 Binary Tree Right Side View – Medium
200 Number of Islands – Medium
Solutions 201 - 250
201 LeetCode Java : Bitwise AND of Numbers Range – Medium
202 LeetCode Java: Happy Number – Easy
203 LeetCode Java: Remove Linked List Elements – Easy
204 LeetCode Java: Count Primes – Easy
205 LeetCode Java: Isomorphic Strings – Easy
206 LeetCode Java: Reverse Linked List -Easy
207 LeetCode Java: Course Schedule – Medium
208 LeetCode Java: Implement Trie (Prefix Tree) – Medium
209 LeetCode Java : Minimum Size Subarray Sum – Medium
210 LeetCode Java: Course Schedule II – Medium
211 LeetCode Java: Add and Search Word – Data structure design – Medium
212 Word Search II
213 House Robber II – Medium
214 Shortest Palindrome
215 Kth Largest Element in an Array – Medium
216 Combination Sum III – Medium
217 Contains Duplicate – Easy
218 The Skyline Problem
219 Contains Duplicate II – Medium
220 Contains Duplicate III – Medium
221 Maximal Square – Medium
222 Count Complete Tree Nodes – Medium
223 Rectangle Area – Easy
224 Basic Calculator
225 Implement Stack using Queues – Easy
226 Invert Binary Tree – Easy
227 Basic Calculator II – Medium
228 Summary Ranges – Medium
229 Majority Element II – Medium
230 Kth Smallest Element in a BST – Medium
231 Power of Two – Easy
232 Implement Queue using Stacks – Easy
234 Palindrome Linked List – Easy
235 Lowest Common Ancestor of a Binary Search Tree – Easy
236 Lowest Common Ancestor of a Binary Tree – Medium
237 Delete Node in a Linked List – Easy
238 Product of Array Except Self – Medium
239 Sliding Window Maximum
240 Search a 2D Matrix II – Medium
241 Different Ways to Add Parentheses – Medium
242 Valid Anagram – Easy
243 Shortest Word Distance – Easy
244 Shortest Word Distance II – Medium
245 Shortest Word Distance III – Medium
246 Strobogrammatic Number – Easy
247 Strobogrammatic Number II
248 LeetCode Java: Different Ways to Add Parentheses – Hard
249 LeetCode Java: Group Shifted Strings – Easy
250 LeetCode Java: Count Univalue Subtrees – Medium
Solutions 251 - 300
251 Flatten 2D Vector
252 LeetCode Java: Meeting Rooms – Easy
253 Meeting Rooms II - Medium
254 Factor Combinations - Medium
255 Verify Preorder Sequence in Binary Search Tree - Medium
256 Paint House - Medium
257 Binary Tree Paths - Easy
258 Add Digits - Easy
259 3Sum Smaller
260 Single Number III
261 Graph Valid Tree
263 Ugly Number
264 Ugly Number II
266 Palindrome Permutation
267 Palindrome Permutation II
268 Missing Number
269 Alien Dictionary
270 Closest Binary Search Tree Value
271 Encode and Decode Strings
272 Closest Binary Search Tree Value II
273 Integer to English Words
274 H-Index
275 H-Index II
276 Paint Fence
277 Find the Celebrity
278 First Bad Version
279 Perfect Squares
280 Wiggle Sort
281 Zigzag Iterator
282 Expression Add Operators
283 Move Zeroes
284 Peeking Iterator
285 Inorder Successor in BST
286 Walls and Gates
288 Unique Word Abbreviation
289 Game of Life
290 Word Pattern
291 Word Pattern II
292 Nim Game
293 Flip Game
294 Flip Game II
295 Find Median from Data Stream
297 Serialize and Deserialize Binary Tree
298 Binary Tree Longest Consecutive Sequence
299 Bulls and Cows
Solutions 301 - 350
301 Remove Invalid Parentheses
302 Smallest Rectangle Enclosing Black Pixels
303 Range Sum Query - Immutable
304 Range Sum Query 2D - Immutable
305 Number of Islands II
306 Additive Number
307 Range Sum Query - Mutable
308 Range Sum Query 2D - Mutable
309 Best Time to Buy and Sell Stock with Cooldown
310 Minimum Height Trees
311 Sparse Matrix Multiplication
312 Burst Balloons
313 Super Ugly Number
314 Binary Tree Vertical Order Traversal
315 Count of Smaller Numbers After Self
316 Remove Duplicate Letters
317 Shortest Distance from All Buildings
318 Maximum Product of Word Lengths
319 Bulb Switcher
320 Generalized Abbreviation
321 Create Maximum Number
322 Coin Change
323 Number of Connected Components in an Undirected Graph
324 Wiggle Sort II
325 Maximum Size Subarray Sum Equals k
326 Power of Three
327 Count of Range Sum
328 Odd Even Linked List
329 Longest Increasing Path in a Matrix
330 Patching Array
331 Verify Preorder Serialization of a Binary Tree
332 Reconstruct Itinerary
333 Largest BST Subtree
334 Increasing Triplet Subsequence
336 Palindrome Pairs
337 House Robber III
338 Counting Bits
339 Nested List Weight Sum
340 Longest Substring with At Most K Distinct Characters
341 Flatten Nested List Iterator
342 Power of Four
343 Integer Break
344 Reverse String
345 Reverse Vowels of a String
346 Moving Average from Data Stream
347 Top K Frequent Elements
348 Design Tic-Tac-Toe
349 Intersection of Two Arrays
350 Intersection of Two Arrays II
Solutions 351 - 400
351 Android Unlock Patterns
353 Design Snake Game
354 Russian Doll Envelopes
355 Design Twitter
356 Line Reflection
357 Count Numbers with Unique Digits
358 Rearrange String k Distance Apart
359 Logger Rate Limiter
360 Sort Transformed Array
361 Bomb Enemy
362 Design Hit Counter
363 Max Sum of Rectangle No Larger Than K
364 Nested List Weight Sum II
365 Water and Jug Problem
366 Find Leaves of Binary Tree
367 Valid Perfect Square
368 Largest Divisible Subset
369 Plus One Linked List
370 Range Addition
371 Sum of Two Integers
372 Super Pow
373 Find K Pairs with Smallest Sums
374 Guess Number Higher or Lower
375 Guess Number Higher or Lower II
377 Combination Sum IV
378 Kth Smallest Element in a Sorted Matrix
379 Design Phone Directory
380 Insert Delete GetRandom O(1)
382 Linked List Random Node
388 Longest Absolute File Path
389 Find the Difference
391 Perfect Rectangle
393 UTF-8 Validation
394 Decode String
397 Integer Replacement
398 Random Pick Index
399 Evaluate Division
400 Nth Digit
Solutions 401 - 450
401 Binary Watch
402 Remove K Digits
404 Sum of Left Leaves
406 Queue Reconstruction by Height
407 Trapping Rain Water II
408 Valid Word Abbreviation
409 Longest Palindrome
411 Minimum Unique Word Abbreviation
415 Add Strings
417 Pacific Atlantic Water Flow
418 Sentence Screen Fitting
421 Maximum XOR of Two Numbers in an Array
422 Valid Word Square
425 Word Squares
444 Sequence Reconstruction
447 Number of Boomerangs
448 Find All Numbers Disappeared in an Array
404 Sum of Left Leaves
410 Split Array Largest Sum
432 All O`one Data Structure
437 Path Sum III
450 Delete Node in a BST
Solutions 451 - 500
451 Sort Characters By Frequency
459 Repeated Substring Pattern
460 LFU Cache
461 Hamming Distance
463 Island Perimeter
465 Optimal Account Balancing
469 Convex Polygon
471 Encode String with Shortest Length
474 Ones and Zeroes
475 Heaters
480 Sliding Window Median
481 Magical String
482 License Key Formatting
483 Smallest Good Base
484 Find Permutation
485 Max Consecutive Ones
486 Predict the Winner
487 Max Consecutive Ones II
490 The Maze
493 Reverse Pairs
494 Target Sum
498 Diagonal Traverse
Solutions 501 - 550
501 Find Mode in Binary Search Tree
503 Next Greater Element II
505 The Maze II
506 Relative Ranks
514 Freedom Trail
515 Find Largest Value in Each Tree Row
520 Detect Capital
521 Longest Uncommon Subsequence I
522 Longest Uncommon Subsequence II
523 Continuous Subarray Sum
524 Longest Word in Dictionary through Deleting
525 Contiguous Array
526 Beautiful Arrangement
527 Word Abbreviation
530 Minimum Absolute Difference in BST
531 Lonely Pixel I
533 Lonely Pixel II
534 Design TinyURL
535 Encode and Decode TinyURL
541 Reverse String II
542 01 Matrix
543 Diameter of Binary Tree
544 Output Contest Matches
545 Boundary of Binary Tree
549 Binary Tree Longest Consecutive Sequence II
516 Longest Palindromic Subsequence
Solutions 551 - 600
551 Student Attendance Record I
552 Student Attendance Record II
560 Subarray Sum Equals K
562 Longest Line of Consecutive One in Matrix
568 Maximum Vacation Days
569 Median Employee Salary
554 Brick Wall
Solutions 601 - 650
621 Task Scheduler
633 Sum of Square Numbers
636 Exclusive Time of Functions
637 Average of Levels in Binary Tree
639 Decode Ways II
642 Design Search Autocomplete System
647 Palindromic Substrings
648 Replace Words
Solutions 651 - 700
653 Two Sum IV - Input is a BST
689 Maximum Sum of 3 Non-Overlapping Subarrays
670 Maximum Swap
671 Second Minimum Node In a Binary Tree
680 Valid Palindrome II
690 Employee Importance
692 Top K Frequent Words
698 Partition to K Equal Sum Subsets
699 Falling Squares
Solutions 701 - 750
714 Best Time to Buy and Sell Stock with Transaction Fee
716 Max Stack
744 Find Smallest Letter Greater Than Target
730 Count Different Palindromic Subsequences
733 Flood Fill
735 Asteroid Collision
Best Time to Buy and Sell Stock
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Solutions 51 - 100
Solutions 51 - 100
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