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README.md

leetcode刷题记录

  • 1 Two Sum | Easy
  • 2 Add Two Numbers|Medium
  • 3 Longest Substring Without Repeating Characters| Medium
  • 4 Median of Two Sorted Arrays|Hard
  • 5 Longest Palindromic Substring|Medium
  • 6 ZigZag Conversion|Medium
  • 7 Reverse Integer|Easy
  • 8 String to Integer (atoi)    Medium
  • 9 Palindrome Number|Easy
  • 10 Regular Expression Matching|Hard
  • 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  |  Medium
  • 20 Valid Parentheses| Easy
  • 21 Merge Two Sorted Lists| Easy
  • 22 Generate Parentheses  |  Medium
  • 23 Merge k Sorted Lists  |  Hard
  • 24 Swap Nodes in Pairs | Medium
  • 25 Reverse Nodes in k-Group  |  Hard
  • 26 Remove Duplicates from Sorted Array | Easy
  • 27 Remove Element| Easy
  • 28 Implement strStr()| Easy
  • 29 Divide Two Integers|Medium
  • 30 Substring with Concatenation of All Words| Hard
  • 31 Next Permutation    Medium
  • 32 Longest Valid Parentheses| Hard
  • 33 Search in Rotated Sorted Array| Medium
  • 34 Search for a Range| Medium
  • 35 Search Insert Position| Easy
  • 36 Valid Sudoku    Medium
  • 37 Sudoku Solver| Hard
  • 38 Count and Say| Easy
  • 39 Combination Sum|Medium
  • 40 Combination Sum II| Medium
  • 41 First Missing Positive| Hard
  • 42 Trapping Rain Water|Hard
  • 43 Multiply Strings    Medium
  • 44 Wildcard Matching| Hard
  • 45 Jump Game II    Hard
  • 46 Permutations    Medium
  • 47 Permutations II | Medium | dfs
  • 48 Rotate Image    Medium
  • 49 Group Anagrams| Medium
  • 50 Pow(x, n)| Medium
  • 51 N-Queens    Hard
  • 52 N-Queens II|Hard
  • 53 Maximum Subarray    Easy
  • 54 Spiral Matrix | Medium
  • 55 Jump Game| Medium
  • 56 Merge Intervals|Medium
  • 57 Insert Interval|Hard
  • 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    Hard
  • 66 Plus One    Easy
  • 67 Add Binary| Easy
  • 68 Text Justification| Hard
  • 69 Sqrt(x)|Easy
  • 70 Climbing Stairs|Easy
  • 71 Simplify Path| Medium
  • 72 Edit Distance| Hard
  • 73 Set Matrix Zeroes| Medium
  • 74 Search a 2D Matrix| Medium
  • 75 Sort Colors|Medium
  • 76 Minimum Window Substring    Hard
  • 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| Medium
  • 82 Remove Duplicates from Sorted List II| Medium
  • 83 Remove Duplicates from Sorted List| Easy
  • 84 Largest Rectangle in Histogram | Hard | Stack
  • 85 Maximal Rectangle| Hard
  • 86 Partition List| Medium
  • 87 Scramble String|Hard
  • 88 Merge Sorted Array| Easy
  • 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
  • 96 Unique Binary Search Trees| Medium
  • 97 Interleaving String|Hard
  • 98 Validate Binary Search Tree|Medium
  • 99 Recover Binary Search Tree| Hard
  • 100 Same Tree| Easy
  • 101 Symmetric Tree| Easy
  • 102 Binary Tree Level Order Traversal| Medium
  • 103 Binary Tree Zigzag Level Order Traversal    Medium
  • 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| Easy
  • 109 Convert Sorted List to Binary Search Tree| Medium
  • 110 Balanced Binary Tree    Easy
  • 111 Minimum Depth of Binary Tree    Easy
  • 112 Path Sum    Easy
  • 113 Path Sum II|Medium
  • 114 Flatten Binary Tree to Linked List| Medium
  • 115 Distinct Subsequences| Hard
  • 116 Populating Next Right Pointers in Each Node|Medium
  • 117 Populating Next Right Pointers in Each Node II| Medium
  • 118 Pascal's Triangle| Easy
  • 119 Pascal's Triangle II    Easy
  • 120 Triangle    Medium
  • 121 Best Time to Buy and Sell Stock|Easy
  • 122 Best Time to Buy and Sell Stock II| Easy
  • 123 Best Time to Buy and Sell Stock III|Hard
  • 124 Binary Tree Maximum Path Sum    Hard
  • 125 Valid Palindrome    Easy
  • 126 Word Ladder II| Hard
  • 127 Word Ladder|Medium
  • 128 Longest Consecutive Sequence    Hard
  • 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
  • 135 Candy| Hard
  • 136 Single Number| Easy
  • 137 Single Number II    Medium
  • 138 Copy List with Random Pointer| Medium
  • 139 Word Break| Medium
  • 140 Word Break II| Hard
  • 141 Linked List Cycle| Easy
  • 142 Linked List Cycle II    Medium
  • 143 Reorder List  |  Medium | LinkedList
  • 144 Binary Tree Preorder Traversal| Medium
  • 145 Binary Tree Postorder Traversal|Hard
  • 146 LRU Cache| Hard
  • 147 Insertion Sort List|Medium
  • 148 Sort List| Medium
  • 149 Max Points on a Line    Hard
  • 150 Evaluate Reverse Polish Notation    Medium
  • 151 Reverse Words in a String| Medium
  • 152 Maximum Product Subarray    Medium
  • 153 Find Minimum in Rotated Sorted Array    Medium
  • 154 Find Minimum in Rotated Sorted Array II|Hard
  • 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 |Hard
  • 159 Longest Substring with At Most Two Distinct Characters |Hard
  • 160 Intersection of Two Linked Lists    Easy
  • 161 One Edit Distance  |Medium
  • 162 Find Peak Element| Medium
  • 163 Missing Ranges |Medium
  • 164 Maximum Gap|Hard
  • 165 Compare Version Numbers|Medium
  • 166 Fraction to Recurring Decimal| Medium
  • 167 Two Sum II - Input array is sorted| Easy
  • 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
  • 174 Dungeon Game    Hard
  • 175 Combine Two Tables| Easy
  • 176 Second Highest Salary| Easy
  • 177 Nth Highest Salary| Medium
  • 178 Rank Scores|Medium
  • 179 Largest Number| Medium
  • 180 Consecutive Numbers|Medium
  • 181 Employees Earning More Than Their Managers| Easy
  • 182 Duplicate Emails    Easy
  • 183 Customers Who Never Order| Easy
  • 184 Department Highest Salary| Medium
  • 185 Department Top Three Salaries| Hard
  • 186 Reverse Words in a String II  | Medium
  • 187 Repeated DNA Sequences| Medium
  • 188 Best Time to Buy and Sell Stock IV| Hard
  • 189 Rotate Array    Easy
  • 190 Reverse Bits    Easy
  • 191 Number of 1 Bits    Easy
  • 192 Word Frequency| Medium
  • 193 Valid Phone Numbers|Easy
  • 194 Transpose File| Medium
  • 195 Tenth Line| Easy
  • 196 Delete Duplicate Emails|Easy
  • 197 Rising Temperature| Easy
  • 198 House Robber    Easy
  • 199 Binary Tree Right Side View|Medium
  • 200 Number of Islands| Medium
  • 201 Bitwise AND of Numbers Range    Medium
  • 202 Happy Number    Easy
  • 203 Remove Linked List Elements|Easy
  • 204 Count Primes    Easy
  • 205 Isomorphic Strings| Easy
  • 206 Reverse Linked List|Easy
  • 207 Course Schedule|Medium
  • 208 Implement Trie (Prefix Tree)    Medium
  • 209 Minimum Size Subarray Sum| Medium
  • 210 Course Schedule II| Medium
  • 211 Add and Search Word - Data structure design|Medium
  • 212 Word Search II| Hard
  • 213 House Robber II|Medium
  • 214 Shortest Palindrome|Hard
  • 215 Kth Largest Element in an Array|Medium
  • 216 Combination Sum III|Medium
  • 217 Contains Duplicate| Easy
  • 218 The Skyline Problem|Hard
  • 219 Contains Duplicate II| Easy
  • 220 Contains Duplicate III| Medium
  • 221 Maximal Square| Medium
  • 222 Count Complete Tree Nodes| Medium
  • 223 Rectangle Area| Medium
  • 224 Basic Calculator    Hard
  • 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
  • 233 Number of Digit One | Hard
  • 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| Hard
  • 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  |Medium
  • 248 Strobogrammatic Number III |Hard
  • 249 Group Shifted Strings  |Medium
  • 250 Count Univalue Subtrees  | Medium
  • 251 Flatten 2D Vector  |Medium
  • 252 Meeting Rooms  |Easy
  • 253 Meeting Rooms II  | Medium
  • 254 Factor Combinations  | Medium
  • 255 Verify Preorder Sequence in Binary Search Tree |Medium
  • 256 Paint House  | Easy
  • 257 Binary Tree Paths| Easy
  • 258 Add Digits| Easy
  • 259 3Sum Smaller  | Medium
  • 260 Single Number III| Medium
  • 261 Graph Valid Tree  | Medium
  • 262 Trips and Users|Hard
  • 263 Ugly Number|Easy
  • 264 Ugly Number II| Medium
  • 265 Paint House II |Hard
  • 266 Palindrome Permutation |Easy
  • 267 Palindrome Permutation II  |Medium
  • 268 Missing Number| Easy
  • 269 Alien Dictionary  | Hard
  • 270 Closest Binary Search Tree Value  | Easy
  • 271 Encode and Decode Strings  |Medium
  • 272 Closest Binary Search Tree Value II  | Hard
  • 273 Integer to English Words    Hard
  • 274 H-Index|Medium
  • 275 H-Index II| Medium
  • 276 Paint Fence  | Easy
  • 277 Find the Celebrity |Medium
  • 278 First Bad Version| Easy
  • 279 Perfect Squares|Medium
  • 280 Wiggle Sort  | Medium
  • 281 Zigzag Iterator  | Medium
  • 282 Expression Add Operators    Hard
  • 283 Move Zeroes|Easy
  • 284 Peeking Iterator    Medium
  • 285 Inorder Successor in BST  | Medium
  • 286 Walls and Gates  | Medium
  • 287 Find the Duplicate Number| Medium
  • 288 Unique Word Abbreviation  | Medium
  • 289 Game of Life    Medium
  • 290 Word Pattern    Easy
  • 291 Word Pattern II  | Hard
  • 292 Nim Game    Easy
  • 293 Flip Game  |Easy
  • 294 Flip Game II  | Medium
  • 295 Find Median from Data Stream    Hard
  • 296 Best Meeting Point |Hard
  • 297 Serialize and Deserialize Binary Tree| Hard
  • 298 Binary Tree Longest Consecutive Sequence  | Medium
  • 299 Bulls and Cows| Medium
  • 300 Longest Increasing Subsequence| Medium
  • 301 Remove Invalid Parentheses| Hard
  • 302 Smallest Rectangle Enclosing Black Pixels  |Hard
  • 303 Range Sum Query - Immutable|Easy
  • 304 Range Sum Query 2D - Immutable| Medium
  • 305 Number of Islands II  | Hard
  • 306 Additive Number|Medium
  • 307 Range Sum Query - Mutable| Medium
  • 308 Range Sum Query 2D - Mutable  | Hard
  • 309 Best Time to Buy and Sell Stock with Cooldown| Medium
  • 310 Minimum Height Trees    Medium
  • 311 Sparse Matrix Multiplication  | Medium
  • 312 Burst Balloons| Hard
  • 313 Super Ugly Number| Medium
  • 314 Binary Tree Vertical Order Traversal  | Medium
  • 315 Count of Smaller Numbers After Self|Hard
  • 316 Remove Duplicate Letters    Hard
  • 317 Shortest Distance from All Buildings  | Hard
  • 318 Maximum Product of Word Lengths|Medium
  • 319 Bulb Switcher| Medium
  • 320 Generalized Abbreviation  | Medium
  • 321 Create Maximum Number| Hard
  • 322 Coin Change|Medium
  • 323 Number of Connected Components in an Undirected Graph  |Medium
  • 324 Wiggle Sort II| Medium
  • 325 Maximum Size Subarray Sum Equals k |Medium
  • 326 Power of Three| Easy
  • 327 Count of Range Sum | Hard | TreeMap
  • 328 Odd Even Linked List    Medium
  • 329 Longest Increasing Path in a Matrix|Hard
  • 330 Patching Array| Hard
  • 331 Verify Preorder Serialization of a Binary Tree| Medium
  • 332 Reconstruct Itinerary| Medium
  • 333 Largest BST Subtree  | Medium
  • 334 Increasing Triplet Subsequence| Medium
  • 335 Self Crossing | Hard
  • 336 Palindrome Pairs    Hard
  • 337 House Robber III    Medium
  • 338 Counting Bits| Medium
  • 339 Nested List Weight Sum |Easy
  • 340 Longest Substring with At Most K Distinct Characters  | Hard
  • 341 Flatten Nested List Iterator    Medium
  • 342 Power of Four| Easy
  • 343 Integer Break| Medium
  • 344 Reverse String| Easy
  • 345 Reverse Vowels of a String| Easy
  • 346 Moving Average from Data Stream       Easy
  • 347 Top K Frequent Elements|Medium
  • 348 Design Tic-Tac-Toe |Medium
  • 349 Intersection of Two Arrays| Easy
  • 350 Intersection of Two Arrays II| Easy
  • 351 Android Unlock Patterns  | Medium
  • 352 Data Stream as Disjoint Intervals| Hard
  • 353 Design Snake Game  |Medium
  • 354 Russian Doll Envelopes| Hard
  • 355 Design Twitter| Medium
  • 356 Line Reflection  | Medium
  • 357 Count Numbers with Unique Digits    Medium
  • 358 Rearrange String k Distance Apart  |Hard
  • 359 Logger Rate Limiter  | Easy
  • 360 Sort Transformed Array |Medium
  • 361 Bomb Enemy |Medium
  • 362 Design Hit Counter |Medium
  • 363 Max Sum of Rectangle No Larger Than K| Hard
  • 364 Nested List Weight Sum II  |Medium
  • 365 Water and Jug Problem| Medium
  • 366 Find Leaves of Binary Tree |Medium
  • 367 Valid Perfect Square    Easy
  • 368 Largest Divisible Subset    Medium
  • 369 Plus One Linked List  | Medium
  • 370 Range Addition |Medium
  • 371 Sum of Two Integers|Easy
  • 372 Super Pow| Medium
  • 373 Find K Pairs with Smallest Sums|Medium
  • 374 Guess Number Higher or Lower    Easy
  • 375 Guess Number Higher or Lower II|Medium
  • 376 Wiggle Subsequence| Medium
  • 377 Combination Sum IV| Medium
  • 378 Kth Smallest Element in a Sorted Matrix|Medium
  • 379 Design Phone Directory |Medium
  • 380 Insert Delete GetRandom O(1)    Medium
  • 381 Insert Delete GetRandom O(1) - Duplicates allowed| Hard
  • 382 Linked List Random Node|Medium
  • 383 Ransom Note|Easy
  • 384 Shuffle an Array    Medium
  • 385 Mini Parser|Medium
  • 386 Lexicographical Numbers|Medium
  • 387 First Unique Character in a String| Easy
  • 388 Longest Absolute File Path| Medium
  • 389 Find the Difference|Easy
  • 390 Elimination Game    Medium
  • 391 Perfect Rectangle| Hard
  • 392 Is Subsequence| Medium
  • 393 UTF-8 Validation    Medium
  • 394 Decode String | Medium | Recursion
  • 395 Longest Substring with At Least K Repeating Characters| Medium
  • 396 Rotate Function|Medium
  • 397 Integer Replacement|Medium
  • 398 Random Pick Index| Medium
  • 399 Evaluate Division| Medium
  • 400 Nth Digit | Easy
  • 401 Binary Watch    Easy
  • 402 Remove K Digits|Medium
  • 403 Frog Jump| Hard
  • 404 Sum of Left Leaves| Easy
  • 405 Convert a Number to Hexadecimal|Easy
  • 406 Queue Reconstruction by Height| Medium
  • 407 Trapping Rain Water II| Hard
  • 408 Valid Word Abbreviation  | Easy
  • 409 Longest Palindrome| Easy
  • 410 Split Array Largest Sum|Hard
  • 411 Minimum Unique Word Abbreviation  | Hard
  • 412 Fizz Buzz| Easy
  • 413 Arithmetic Slices| Medium
  • 414 Third Maximum Number    Easy
  • 415 Add Strings|Easy
  • 416 Partition Equal Subset Sum| Medium
  • 417 Pacific Atlantic Water Flow|Medium
  • 418 Sentence Screen Fitting  | Medium
  • 419 Battleships in a Board| Medium
  • 420 Strong Password Checker|Hard
  • 421 Maximum XOR of Two Numbers in an Array| Medium
  • 422 Valid Word Square  |Easy
  • 423 Reconstruct Original Digits from English   | Medium
  • 424 Longest Repeating Character Replacement|Medium
  • 425 Word Squares  | Hard
  • 430 Flatten a Multilevel Doubly Linked List | Medium
  • 432 All O`one Data Structure    Hard
  • 433 Minimum Genetic Mutation    Medium
  • 434 Number of Segments in a String| Easy
  • 435 Non-overlapping Intervals| Medium
  • 436 Find Right Interval | Medium
  • 437 Path Sum III   | Easy
  • 438 Find All Anagrams in a String | Easy
  • 439 Ternary Expression Parser  | Medium
  • 440 K-th Smallest in Lexicographical Order| Hard
  • 441 Arranging Coins|Easy
  • 442 Find All Duplicates in an Array|Medium
  • 444 Sequence Reconstruction  | Medium
  • 445 Add Two Numbers II| Medium
  • 446 Arithmetic Slices II - Subsequence| Hard
  • 447 Number of Boomerangs    Easy
  • 448 Find All Numbers Disappeared in an Array    Easy
  • 449 Serialize and Deserialize BST| Medium
  • 450 Delete Node in a BST  |  Medium
  • 451 Sort Characters By Frequency    Medium
  • 452 Minimum Number of Arrows to Burst Balloons| Medium
  • 453 Minimum Moves to Equal Array Elements| Easy
  • 454 4Sum II|Medium
  • 455 Assign Cookies| Easy
  • 456 132 Pattern|Medium
  • 457 Circular Array Loop|Medium
  • 458 Poor Pigs| Easy
  • 459 Repeated Substring Pattern| Easy
  • 460 LFU Cache| Hard
  • 461 Hamming Distance    Easy
  • 462 Minimum Moves to Equal Array Elements II    Medium
  • 463 Island Perimeter  |  Easy
  • 464 Can I Win | Medium
  • 465 Optimal Account Balancing  |Hard
  • 466 Count The Repetitions| Hard
  • 467 Unique Substrings in Wraparound String| Medium
  • 468 Validate IP Address|Medium
  • 469 Convex Polygon |Medium
  • 470 Implement Rand10() Using Rand7() | Medium
  • 471 Encode String with Shortest Length |Hard
  • 472 Concatenated Words| Hard
  • 473 Matchsticks to Square| Medium
  • 474 Ones and Zeroes|Medium
  • 475 Heaters|Easy
  • 476 Number Complement| Easy
  • 477 Total Hamming Distance| Medium
  • 478 Generate Random Point in a Circle | Medium
  • 479 Largest Palindrome Product| Easy
  • 480 Sliding Window Median| Hard
  • 481 Magical String| Medium
  • 482 License Key Formatting| Medium
  • 483 Smallest Good Base| Hard
  • 484 Find Permutation  | Medium
  • 485 Max Consecutive Ones    Easy
  • 486 Predict the Winner| Medium
  • 487 Max Consecutive Ones II  | Medium
  • 488 Zuma Game| Hard
  • 490 The Maze  | Medium
  • 491 Increasing Subsequences | Medium
  • 492 Construct the Rectangle|Easy
  • 493 Reverse Pairs| Hard
  • 494 Target Sum| Medium
  • 495 Teemo Attacking|Medium
  • 496 Next Greater Element I| Easy
  • 498 Diagonal Traverse| Medium
  • 499 The Maze III  | Hard
  • 500 Keyboard Row    Easy
  • 501 Find Mode in Binary Search Tree|Easy
  • 502 IPO|Hard
  • 503 Next Greater Element II | Medium
  • 504 Base 7| Easy
  • 505 The Maze II  | Medium
  • 506 Relative Ranks| Easy
  • 507 Perfect Number| Easy
  • 508 Most Frequent Subtree Sum| Medium
  • 513 Find Bottom Left Tree Value|Medium
  • 514 Freedom Trail| Hard
  • 515 Find Largest Value in Each Tree Row|Medium
  • 516 Longest Palindromic Subsequence|Medium
  • 517 Super Washing Machines| Hard
  • 518 Coin Change 2 | Medium
  • 519 Random Flip Matrix | Medium
  • 520 Detect Capital| Easy
  • 521 Longest Uncommon Subsequence I |Easy
  • 522 Longest Uncommon Subsequence II|Medium
  • 523 Continuous Subarray Sum|Medium
  • 524 Longest Word in Dictionary through Deleting|Medium
  • 525 Contiguous Array    Medium
  • 526 Beautiful Arrangement| Medium
  • 527 Word Abbreviation  |Hard
  • 529 Minesweeper|Medium
  • 530 Minimum Absolute Difference in BST| Easy
  • 531 Lonely Pixel I |Medium
  • 532 K-diff Pairs in an Array    Easy
  • 533 Lonely Pixel II  | Medium
  • 534 Design TinyURL| Medium
  • 535 Encode and Decode TinyURL| Medium
  • 536 Construct Binary Tree from String  |Medium
  • 537 Complex Number Multiplication| Medium
  • 538 Convert BST to Greater Tree|Easy
  • 539 Minimum Time Difference|Medium
  • 540 Single Element in a Sorted Array    Medium
  • 541 Reverse String II | Easy
  • 542 01 Matrix| Medium
  • 543 Diameter of Binary Tree|Easy
  • 544 Output Contest Matches |Medium
  • 545 Boundary of Binary Tree  | Medium
  • 546 Remove Boxes    Hard
  • 547 Friend Circles| Medium
  • 548 Split Array with Equal Sum |Medium
  • 549 Binary Tree Longest Consecutive Sequence II  | Medium
  • 551 Student Attendance Record I|Easy
  • 552 Student Attendance Record II    Hard
  • 553 Optimal Division    Medium
  • 554 Brick Wall | Medium
  • 555 Split Concatenated Strings |Medium
  • 556 Next Greater Element III  |  Medium
  • 557 Reverse Words in a String III| Easy
  • 559 Maximum Depth of N-ary Tree | Easy
  • 560 Subarray Sum Equals K| Medium
  • 561 Array Partition I| Easy
  • 562 Longest Line of Consecutive One in Matrix  |Medium
  • 563 Binary Tree Tilt    Easy
  • 564 Find the Closest Palindrome|Hard
  • 566 Reshape the Matrix| Easy
  • 567 Permutation in String| Medium
  • 568 Maximum Vacation Days  |Hard
  • 569 Median Employee Salary |Hard
  • 570 Managers with at Least 5 Direct Reports  | Medium
  • 571 Find Median Given Frequency of Numbers |Hard
  • 572 Subtree of Another Tree|Easy
  • 573 Squirrel Simulation  | Medium
  • 574 Winning Candidate  |Medium
  • 575 Distribute Candies| Easy
  • 576 Out of Boundary Paths| Medium
  • 577 Employee Bonus |Easy
  • 578 Get Highest Answer Rate Question  | Medium
  • 579 Find Cumulative Salary of an Employee  |Hard
  • 580 Count Student Number in Departments  | Medium
  • 581 Shortest Unsorted Continuous Subarray| Easy
  • 582 Kill Process  | Medium
  • 583 Delete Operation for Two Strings    Medium
  • 584 Find Customer Referee  |Easy
  • 585 Investments in 2016  | Medium
  • 586 Customer Placing the Largest Number of Orders  |Easy
  • 587 Erect the Fence|Hard
  • 588 Design In-Memory File System  | Hard
  • 590 N-ary Tree Postorder Traversal | Easy
  • 591 Tag Validator| Hard
  • 592 Fraction Addition and Subtraction| Medium
  • 593 Valid Square  |  Medium
  • 594 Longest Harmonious Subsequence| Easy
  • 595 Big Countries| Easy
  • 596 Classes More Than 5 Students    Easy
  • 597 Friend Requests I: Overall Acceptance Rate |Easy
  • 598 Range Addition II| Easy
  • 599 Minimum Index Sum of Two Lists| Easy
  • 600 Non-negative Integers without Consecutive Ones| Hard
  • 601 Human Traffic of Stadium    Hard
  • 602 Friend Requests II: Who Has the Most Friends  | Medium
  • 603 Consecutive Available Seats  | Easy
  • 604 Design Compressed String Iterator  |Easy
  • 605 Can Place Flowers| Easy
  • 606 Construct String from Binary Tree| Easy
  • 607 Sales Person  | Easy
  • 608 Tree Node  |Medium
  • 609 Find Duplicate File in System| Medium
  • 610 Triangle Judgement  | Easy
  • 611 Valid Triangle Number | Medium
  • 612 Shortest Distance in a Plane  | Medium
  • 613 Shortest Distance in a Line  | Easy
  • 614 Second Degree Follower |Medium
  • 615 Average Salary: Departments VS Company |Hard
  • 616 Add Bold Tag in String |Medium
  • 617 Merge Two Binary Trees| Easy
  • 618 Students Report By Geography  | Hard
  • 619 Biggest Single Number  |Easy
  • 620 Not Boring Movies| Easy
  • 621 Task Scheduler| Medium
  • 623 Add One Row to Tree|Medium
  • 624 Maximum Distance in Arrays |Easy
  • 625 Minimum Factorization  |Medium
  • 626 Exchange Seats| Medium
  • 627 Swap Salary|Easy
  • 628 Maximum Product of Three Numbers    Easy
  • 629 K Inverse Pairs Array| Hard
  • 630 Course Schedule III | Hard | Greedy
  • 631 Design Excel Sum Formula  | Hard
  • 632 Smallest Range| Hard
  • 633 Sum of Square Numbers| Easy
  • 634 Find the Derangement of An Array  | Medium
  • 635 Design Log Storage System  |Medium
  • 636 Exclusive Time of Functions|Medium
  • 637 Average of Levels in Binary Tree    Easy
  • 638 Shopping Offers|Medium
  • 639 Decode Ways II| Hard
  • 640 Solve the Equation | Medium
  • 641 Design Circular Deque.md | Medium
  • 642 Design Search Autocomplete System  |Hard
  • 643 Maximum Average Subarray I| Easy
  • 644 Maximum Average Subarray II  | Hard
  • 645 Set Mismatch  |  Easy
  • 646 Maximum Length of Pair Chain    Medium
  • 647 Palindromic Substrings| Medium
  • 648 Replace Words| Medium
  • 649 Dota2 Senate    Medium
  • 650 2 Keys Keyboard | Medium
  • 651 4 Keys Keyboard  | Medium
  • 652 Find Duplicate Subtrees | Medium
  • 653 Two Sum IV - Input is a BST|Easy
  • 654 Maximum Binary Tree|Medium
  • 655 Print Binary Tree | Medium
  • 656 Coin Path  |Hard
  • 657 Judge Route Circle| Easy
  • 658 Find K Closest Elements | Medium
  • 659 Split Array into Consecutive Subsequences| Medium
  • 660 Remove 9  | Hard
  • 661 Image Smoother| Easy
  • 662 Maximum Width of Binary Tree    Medium
  • 663 Equal Tree Partition  | Medium
  • 664 Strange Printer|Hard
  • 665 Non-decreasing Array    Easy
  • 666 Path Sum IV  | Medium
  • 667 Beautiful Arrangement II    Medium
  • 668 Kth Smallest Number in Multiplication Table | Hard
  • 669 Trim a Binary Search Tree| Easy
  • 670 Maximum Swap    Medium
  • 671 Second Minimum Node In a Binary Tree    Easy
  • 672 Bulb Switcher II  |  Medium
  • 673 Number of Longest Increasing Subsequence    Medium
  • 674 Longest Continuous Increasing Subsequence| Easy
  • 675 Cut Off Trees for Golf Event    Hard
  • 676 Implement Magic Dictionary| Medium
  • 677 Map Sum Pairs| Medium
  • 678 Valid Parenthesis String  | Medium
  • 679 24 Game|Hard
  • 680 Valid Palindrome II|Easy
  • 681 Next Closest Time| Medium
  • 682 Baseball Game| Easy
  • 683 K Empty Slots| Hard
  • 684 Redundant Connection    Medium
  • 685 Redundant Connection II|Hard
  • 686 Repeated String Match | Easy
  • 687 Longest Univalue Path | Easy
  • 688 Knight Probability in Chessboard  |   Medium
  • 689 Maximum Sum of 3 Non-Overlapping Subarrays| Hard
  • 690 Employee Importance|Easy
  • 691 Stickers to Spell Word| Hard
  • 692 Top K Frequent Words  |  Medium
  • 693 Binary Number with Alternating Bits|Easy
  • 694 Number of Distinct Islands |Medium
  • 695 Max Area of Island| Easy
  • 696 Count Binary Substrings|Easy
  • 697 Degree of an Array| Easy
  • 698 Partition to K Equal Sum Subsets    Medium
  • 699 Falling Squares|Hard
  • 703 Kth Largest Element in a Stream | Easy
  • 704 Binary Search | Easy
  • 705 Design HashSet | Easy
  • 706. Design HashMap | Easy
  • 711 Number of Distinct Islands II  |Hard
  • 712 Minimum ASCII Delete Sum for Two Strings    Medium
  • 713 Subarray Product Less Than K    Medium
  • 714 Best Time to Buy and Sell Stock with Transaction Fee|Medium
  • 715 Range Module|Hard
  • 716 Max Stack|Hard
  • 717 1-bit and 2-bit Characters|Easy
  • 718 Maximum Length of Repeated Subarray|Medium
  • 719 Find K-th Smallest Pair Distance|Hard
  • 720 Longest Word in Dictionary | Easy
  • 721 Accounts Merge|Medium
  • 722 Remove Comments|Medium
  • 723 Candy Crush|Medium
  • 724 Find Pivot Index|Easy
  • 725 Split Linked List in Parts|Medium
  • 726 Number of Atoms | Hard | Recursion
  • 727 Minimum Window Subsequence|Hard
  • 728 Self Dividing Numbers|Easy
  • 729 My Calendar I|Medium
  • 730 Count Different Palindromic Subsequences|Hard
  • 731 My Calendar II|Medium
  • 732 My Calendar III|Hard
  • 733 Flood Fill|Easy
  • 734 Sentence Similarity|Easy
  • 735 Asteroid Collision|Medium
  • 736 Parse Lisp Expression|Hard
  • 737 Sentence Similarity II|Medium
  • 738 Monotone Increasing Digits|Medium
  • 739 Daily Temperatures|Medium
  • 740 Delete and Earn|Medium
  • 741 Cherry Pickup|Hard
  • 742 Closest Leaf in a Binary Tree|Medium
  • 743 Network Delay Time|Medium
  • 744 Find Smallest Letter Greater Than Target|Easy
  • 745 Prefix and Suffix Search|Hard
  • 746 Min Cost Climbing Stairs|Easy
  • 747 Largest Number At Least Twice of Others|Easy
  • 748 Shortest Completing Word|Medium
  • 749 Contain Virus|Hard
  • 750 Number Of Corner Rectangles|Medium
  • 751 IP to CIDR|Easy
  • 752 Open the Lock|Medium
  • 753 Cracking the Safe|Hard
  • 754 Reach a Number | Easy
  • 755 Pour Water|Medium
  • 756 Pyramid Transition Matrix |Medium
  • 757 Set Intersection Size At Least Two|Hard
  • 758 Bold Words in String|Easy
  • 759 Employee Free Time|Hard
  • 760 Find Anagram Mappings|Easy
  • 761 Special Binary String|Hard
  • 762 Prime Number of Set Bits in Binary Representation|Easy
  • 763 Partition Labels | Medium
  • 764 Largest Plus Sign|Medium
  • 765 Couples Holding Hands|Hard
  • 766 Toeplitz Matrix|Easy
  • 767 Reorganize String|Medium
  • 768 Max Chunks To Make Sorted II|Hard
  • 769 Max Chunks To Make Sorted|Medium
  • 770 Basic Calculator IV|Hard
  • 771 Jewels and Stones|Easy
  • 772 Basic Calculator III|Hard
  • 773 Sliding Puzzle|Hard
  • 774 Minimize Max Distance to Gas Station|Hard
  • 775 Global and Local Inversions|Medium
  • 776 Split BST|Medium
  • 777 Swap Adjacent in LR String|Medium
  • 778 Swim in Rising Water|Hard
  • 779 K-th Symbol in Grammar|Medium
  • 780 Reaching Points|Hard
  • 781 Rabbits in Forest|Medium
  • 782 Transform to Chessboard|Hard
  • 783 Minimum Distance Between BST Nodes|Easy
  • 784 Letter Case Permutation|Easy
  • 785 Is Graph Bipartite?|Medium
  • 786 K-th Smallest Prime Fraction | Hard
  • 787 Cheapest Flights Within K Stops|Medium
  • 788 Rotated Digits    New Easy
  • 789 Escape The Ghosts    New Medium
  • 790 Domino and Tromino Tiling | Medium | dp
  • 791 Custom Sort String  |  Medium
  • 792 Number of Matching Subsequences | Medium
  • 793 Preimage Size of Factorial Zeroes Function | Hard
  • 795 Number of Subarrays with Bounded Maximum | Medium
  • 796 Rotate String|Easy
  • 797 All Paths From Source to Target | Medium
  • 802 Find Eventual Safe States | Medium
  • 804 Unique Morse Code Words | Easy
  • 805 Split Array With Same Average | Hard
  • 806 Number of Lines To Write String | Easy
  • 807 Max Increase to Keep City Skyline | Medium
  • 808 Soup Servings | Medium
  • 812 Largest Triangle Area | Easy
  • 816 Ambiguous Coordinates | Medium
  • 817 Linked List Components | Medium | HashSet
  • 819 Most Common Word | Easy
  • 820 Short Encoding of Words | Medium
  • 821 Shortest Distance to a Character | Easy
  • 824 Goat Latin | Easy
  • 826 Most Profit Assigning Work|Medium
  • 830 Positions of Large Groups | Easy
  • 832 Flipping an Image | Easy
  • 835 Image Overlap | Medium
  • 836 Rectangle Overlap | Easy
  • 837 New 21 Game | Medium
  • 844 Backspace String Compare| Easy
  • 845 Longest Mountain in Array | Medium
  • 846 Hand of Straights | Medium
  • 848 Shifting Letters | Medium
  • 849 Maximize Distance to Closest Person | Easy
  • 851 Loud and Rich | Medium
  • 852 Peak Index in a Mountain Array|Easy
  • 853 Car Fleet | Medium
  • 856 Score of Parentheses | Medium
  • 858 Mirror Reflection | Medium
  • 859 Buddy Strings | Easy
  • 860 Lemonade Change | Medium
  • 861 Score After Flipping Matrix | Medium
  • 863 All Nodes Distance K in Binary Tree | Medium
  • 865 Smallest Subtree with all the Deepest Nodes | Medium
  • 866 Prime Palindrome | Medium
  • 867 Transpose Matrix | Easy
  • 868 Binary Gap | Easy
  • 869 Reordered Power of 2 | Medium
  • 870 Advantage Shuffle | Medium
  • 872 Leaf-Similar Trees | Easy
  • 873 Length of Longest Fibonacci Subsequence | Medium
  • 875 Koko Eating Bananas | Medium
  • 876 Middle of the Linked List | Easy
  • 877 Stone Game | Medium
  • 878 Nth Magical Number | Hard
  • 881 Boats to Save People | Medium
  • 883 Projection Area of 3D Shapes | Easy
  • 884 Uncommon Words from Two Sentences | Easy
  • 885 Spiral Matrix III | Medium
  • 896 Possible Bipartition | Medium
  • 888 Fair Candy Swap | Easy
  • 890 Find and Replace Pattern | Medium
  • 892 Surface Area of 3D Shapes | Easy
  • 893 Groups of Special-Equivalent Strings | Easy
  • 894 All Possible Full Binary Trees | Medium
  • 896 Monotonic Array | Easy
  • 897 Increasing Order Search Tree | Easy
  • 899 Orderly Queue | Hard
  • 904 Fruit Into Baskets | Medium
  • 905 Sort Array By Parity | Easy
  • 908 Smallest Range I | Easy
  • 919 Complete Binary Tree Inserter | Tree
  • 910 Smallest Range II | Medium
  • 911 Online Election | Medium
  • 914 X of a Kind in a Deck of Cards | Easy
  • 915 Partition Array into Disjoint Intervals | Medium
  • 916 Word Subsets | Medium
  • 917 Reverse Only Letters | Easy
  • 918 Maximum Sum Circular Subarray | Medium
  • 921 Minimum Add to Make Parentheses Valid | Medium
  • 922 Sort Array By Parity II | Easy
  • 923 3Sum With Multiplicity | Medium
  • 925 Long Pressed Name | Easy
  • 926 Flip String to Monotone Increasing | Medium
  • 927 Three Equal Parts | Hard |
  • 930 Binary Subarrays With Sum | Medium
  • 931 Minimum Falling Path Sum | Medium | Dp
  • 933 Number of Recent Calls | Easy
  • 935 Knight Dialer | Medium
  • 938 Range Sum of BST | Medium
  • 941. Valid Mountain Array | Easy
  • 942 DI String Match | Easy
  • 944 Delete Columns to Make Sorted | Medium
  • 946 Validate Stack Sequences | Medium
  • 947 Most Stones Removed with Same Row or Column | Medium
  • 949 Largest Time for Given Digits | Easy
  • 950 Reveal Cards In Increasing Order | Medium
  • 951 Flip Equivalent Binary Trees | Medium
  • 953 Verifying an Alien Dictionary | Easy
  • 954 Array of Doubled Pairs | Medium
  • 955 Delete Columns to Make Sorted II | Medium
  • 957 Prison Cells After N Days | Medium
  • 960 Delete Columns to Make Sorted III | Hard
  • 961 N-Repeated Element in Size 2N Array | Easy
  • 965 Univalued Binary Tree | Easy
  • 969 Pancake Sorting |Medium
  • 970 Powerful Integers | Easy
  • 973 K Closest Points to Origin | Easy
  • 975 Odd Even Jump | Hard
  • 976 Largest Perimeter Triangle | Easy
  • 977 Squares of a Sorted Array | Easy
  • 979 Distribute Coins in Binary Tree | Medium
  • 983 Minimum Cost For Tickets | Medium
  • 982 Triples with Bitwise AND Equal To Zero | Hard
  • 984 String Without AAA or BBB | Easy
  • 985 Sum of Even Numbers After Queries | Easy
  • 986 Interval List Intersections | Medium
  • 988 Smallest String Starting From Leaf | Medium
  • 987 Vertical Order Traversal of a Binary Tree | Medium
  • 993 Cousins in Binary Tree | Easy
  • 994 Rotting Oranges | Easy | BFS
  • 995 Minimum Number of K Consecutive Bit Flips | Medium
  • 997 Find the Town Judge | Easy
  • 998 Maximum Binary Tree II | Medium
  • 1002 Find Common Characters | Easy
  • 1003 Check If Word Is Valid After Substitutions | Medium
  • 1004 Max Consecutive Ones III | Medium
  • 1005 Maximize Sum Of Array After K Negations | Easy
  • 1006 Clumsy Factorial | Medium
  • 1008 Construct Binary Search Tree from Preorder Traversal | Medium
  • 1010 Pairs of Songs With Total Durations Divisible by 60 | Easy
  • 1016 Binary String With Substrings Representing 1 To N | Medium
  • 1017 Convert to Base -2 | Medium
  • 1018 Binary Prefix Divisible By 5 | Easy
  • 1021 Remove Outermost Parentheses | Easy | Stack
  • 1022 Sum of Root To Leaf Binary Numbers | Easy
  • 1025 Divisor Game | Easy
  • 1029 Two City Scheduling | Easy
  • 1031 Maximum Sum of Two Non-Overlapping Subarrays | Medium
  • 1035 Uncrossed Lines | Medium
  • 1041 Robot Bounded In Circle | Easy
  • 1043 Partition Array for Maximum Sum | Medium
  • 1046 Last Stone Weight | Easy | PriorityQueue
  • 1047 Remove All Adjacent Duplicates In String | Easy | Stack
  • 1048. Longest String Chain | Medium | dp
  • 1051 Height Checker | Easy
  • 1052 Grumpy Bookstore Owner | Medium
  • 1053 Previous Permutation With One Swap | Medium
  • 1071 Greatest Common Divisor of Strings | Easy
  • 1081 Smallest Subsequence of Distinct Characters | Medium
  • 1089 Duplicate Zeros | Easy
  • 1090 Largest Values From Labels | Medium | greedy
  • 1091 Shortest Path in Binary Matrix | Medium | BFS
  • 1092 Shortest Common Supersequence | Hard | Dp
  • 1103 Distribute Candies to People | Easy
  • 1104 Path In Zigzag Labelled Binary Tree
  • 1108 Defanging an IP Address | Easy
  • 1110 Delete Nodes And Return Forest | Medium | Tree
  • 1111 Maximum Nesting Depth of Two Valid Parentheses Strings | Medium
  • 1114 Print in Order | Easy| MultiThread
  • 1128 Number of Equivalent Domino Pairs | Easy
  • 1154 Day of the Year | Easy
  • 1161 Maximum Level Sum of a Binary Tree | Medium | Tree
  • 5083 Occurrences After Bigram | Easy
  • 5084 Insufficient Nodes in Root to Leaf Paths | Medium | Tree
  • 5087 Letter Tile Possibilities | Medium
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