README.md

LeetCode

The number of LeetCode questions is increasing every week. For more questions and solutions, you can see my LintCode repository. I'll keep updating for full summary and better solutions. Stay tuned for updates. (Notes: "?" means you need to subscribe to LeetCode premium membership for the access to premium questions.)

Algorithms

Database

Shell

Shell Script

Bit Manipulation

# Title Solution Time Space Difficulty Tag Note 136 Single Number C++ Python O(n) O(1) Easy

137 Single Number II C++ Python O(n) O(1) Medium

190 Reverse Bits C++ Python O(1) O(1) Easy

191 Number of 1 Bits C++ Python O(1) O(1) Easy

201 Bitwise AND of Numbers Range C++ Python O(1) O(1) Medium

231 Power of Two C++ Python O(1) O(1) Easy LintCode

260 Single Number III C++ Python O(n) O(1) Medium

268 Missing Number C++ Python O(n) O(1) Medium LintCode

318 Maximum Product of Word Lengths C++ Python O(n) ~ O(n^2) O(n) Medium

Bit Manipulation, Counting Sort, Pruning 342 Power of Four C++ Python O(1) O(1) Easy

371 Sum of Two Integers C++ Python O(1) O(1) Easy LintCode

389 Find the Difference C++ Python O(n) O(1) Easy

393 UTF-8 Validation C++ Python O(n) O(1) Medium

401 Binary Watch C++ Python O(1) O(1) Easy

411 Minimum Unique Word Abbreviation C++ Python O(2^n) O(n) Hard ?

421 Maximum XOR of Two Numbers in an Array C++ Python O(n) O(1) Medium

461 Hamming Distance C++ Python O(1) O(1) Easy

462 Minimum Moves to Equal Array Elements II C++ Python O(n) on average O(1) Medium

477 Total Hamming Distance C++ Python O(n) O(1) Medium

645 Set Mismatch C++ Python O(n) O(1) Easy

693 Binary Number with Alternating Bits C++ Python O(1) O(1) Easy

762 Prime Number of Set Bits in Binary Representation C++ Python O(1) O(1) Easy

Array

# Title Solution Time Space Difficulty Tag Note 015 3 Sum C++ Python O(n^2) O(1) Medium

Two Pointers 016 3 Sum Closest C++ Python O(n^2) O(1) Medium

Two Pointers 018 4 Sum C++ Python O(n^3) O(1) Medium

Two Pointers 026 Remove Duplicates from Sorted Array C++ Python O(n) O(1) Easy

Two Pointers 027 Remove Element C++ Python O(n) O(1) Easy

031 Next Permutation C++ Python O(n) O(1) Medium

Tricky 041 First Missing Positive C++ Python O(n) O(1) Hard

Tricky 048 Rotate Image C++ Python O(n^2) O(1) Medium

054 Spiral Matrix C++ Python O(m * n) O(1) Medium

059 Spiral Matrix II C++ Python O(n^2) O(1) Medium

066 Plus One C++ Python O(n) O(1) Easy

073 Set Matrix Zeroes C++ Python O(m * n) O(1) Medium

080 Remove Duplicates from Sorted Array II C++ Python O(n) O(1) Medium

Two Pointers 118 Pascal's Triangle C++ Python O(n^2) O(1) Easy

119 Pascal's Triangle II C++ Python O(n^2) O(1) Easy

121 Best Time to Buy and Sell Stock C++ Python O(n) O(1) Easy

128 Longest Consecutive Sequence C++ Python O(n) O(n) Hard

Tricky 157 Read N Characters Given Read4 C++ Python O(n) O(1) Easy ?

158 Read N Characters Given Read4 II - Call multiple times C++ Python O(n) O(1) Hard ?

163 Missing Ranges C++ Python O(n) O(1) Medium ?

169 Majority Element C++ Python O(n) O(1) Easy

189 Rotate Array C++ Python O(n) O(1) Easy

209 Minimum Size Subarray Sum C++ Python O(n) O(1) Medium

Binary Search 215 Kth Largest Element in an Array C++ Python O(n) ~ O(n^2) O(1) Medium EPI

228 Summary Ranges C++ Python O(n) O(1) Medium

229 Majority Element II C++ Python O(n) O(1) Medium

238 Product of Array Except Self C++ Python O(n) O(1) Medium LintCode

240 Search a 2D Matrix II C++ Python O(m + n) O(1) Medium EPI, LintCode

243 Shortest Word Distance C++ Python O(n) O(1) Easy ?

245 Shortest Word Distance III C++ Python O(n) O(1) Medium ?

251 Flatten 2D Vector C++ Python O(1) O(1) Medium ?

277 Find the Celebrity C++ Python O(n) O(1) Medium ?, EPI

289 Game of Life C++ Python O(m * n) O(1) Medium

293 Flip Game C++ Python O(n * (c+1)) O(1) Easy ?

296 Best Meeting Point C++ Python O(m * n) O(m + n) Hard ?

311 Sparse Matrix Multiplication C++ Python O(m * n * l) O(m * l) Medium ?

334 Increasing Triplet Subsequence C++ Python O(n) O(1) Medium

370 Range Addition C++ Python O(k + n) O(1) Medium ?

384 Shuffle an Array C++ Python O(n) O(n) Medium EPI

396 Rotate Function C++ Python O(n) O(1) Easy

412 Fizz Buzz C++ Python O(n) O(1) Easy

414 Third Maximum Number C++ Python O(n) O(1) Easy

419 Battleships in a Board C++ Python O(m * n) O(1) Medium

422 Valid Word Square C++ Python O(m * n) O(1) Easy ?

442 Find All Duplicates in an Array C++ Python O(n) O(1) Medium

448 Find All Numbers Disappeared in an Array C++ Python O(n) O(1) Easy

531 Lonely Pixel I C++ Python O(m * n) O(m + n) Medium ?

533 Lonely Pixel II C++ Python O(m * n) O(m * n) Medium ?

565 Array Nesting C++ Python O(n) O(1) Medium

566 Reshape the Matrix C++ Python O(m * n) O(m * n) Easy

581 Shortest Unsorted Continuous Subarray C++ Python O(n) O(1) Easy

605 Can Place Flowers C++ Python O(n) O(1) Easy

624 Maximum Distance in Arrays C++ Python O(n) O(1) Easy ?

643 Maximum Average Subarray I C++ Python O(n) O(1) Easy

Math 644 Maximum Average Subarray II C++ Python O(n) O(n) Hard ? Math 661 Image Smoother C++ Python O(m * n) O(1) Easy

665 Non-decreasing Array C++ Python O(n) O(1) Easy

667 Beautiful Arrangement II C++ Python O(n) O(1) Medium

670 Maximum Swap C++ Python O(logn) O(logn) Medium

674 Longest Continuous Increasing Subsequence C++ Python O(n) O(1) Easy

683 K Empty Slots C++ Python O(n) O(n) Hard

697 Degree of an Array C++ Python O(n) O(n) Easy

713 Subarray Product Less Than K C++ Python O(n) O(1) Medium

717 1-bit and 2-bit Characters C++ Python O(n) O(1) Easy

Greedy 723 Candy Crush C++ Python O((R * C)^2) O(1) Medium

724 Find Pivot Index C++ Python O(n) O(1) Easy

729 My Calendar I C++ Python O(nlogn) O(n) Medium

731 My Calendar II C++ Python O(n^2) O(n) Medium

732 My Calendar III C++ Python O(n^2) O(n) Hard

747 Largest Number At Least Twice of Others C++ Python O(n) O(1) Easy

755 Pour Water C++ Python O(v * n) O(1) Medium

766 Toeplitz Matrix C++ Python O(m * n) O(1) Easy

768 Max Chunks To Make Sorted II C++ Python O(nlogn) O(n) Hard

769 Max Chunks To Make Sorted C++ Python O(n) O(1) Medium

778 Swim in Rising Water C++ Python O(n^2) O(n^2) Hard

Union Find 792 Number of Matching Subsequences C++ Python O(n + w) O(1) Medium

794 Valid Tic-Tac-Toe State C++ Python O(1) O(1) Medium

795 Number of Subarrays with Bounded Maximum C++ Python O(n) O(1) Medium

String

# Title Solution Time Space Difficulty Tag Note 005 Longest Palindromic Substring C++ Python O(n) O(n) Medium

Manacher's Algorithm 006 ZigZag Conversion C++ Python O(n) O(1) Easy

008 String to Integer (atoi) C++ Python O(n) O(1) Easy

014 Longest Common Prefix C++ Python O(n * k) O(1) Easy

028 Implement strStr() C++ Python O(n + k) O(k) Easy

KMP Algorithm 038 Count and Say C++ Python O(n * 2^n) O(2^n) Easy

043 Multiply Strings C++ Python O(m * n) O(m + n) Medium

058 Length of Last Word C++ Python O(n) O(1) Easy

067 Add Binary C++ Python O(n) O(1) Easy

068 Text Justification C++ Python O(n) O(1) Hard

125 Valid Palindrome C++ Python O(n) O(1) Easy

151 Reverse Words in a String C++ Python O(n) O(1) Medium

161 One Edit Distance C++ Python O(m + n) O(1) Medium ?

165 Compare Version Numbers C++ Python O(n) O(1) Easy

186 Reverse Words in a String II C++ Python O(n) O(1) Medium ?

214 Shortest Palindrome C++ Python O(n) O(n) Hard

KMP Algorithm Manacher's Algorithm 242 Valid Anagram C++ Python O(n) O(1) Easy LintCode

271 Encode and Decode Strings C++ Python O(n) O(1) Medium ?

273 Integer to English Words C++ Python O(1) O(1) Hard

306 Addictive Number C++ Python O(n^3) O(n) Medium

383 Ransom Note C++ Python O(n) O(1) Easy EPI

405 Convert a Number to Hexadecimal C++ Python O(n) O(1) Easy

408 Valid Word Abbreviation C++ Python O(n) O(1) Easy ?

415 Add Strings C++ Python O(n) O(1) Easy

420 Strong Password Checker C++ Python O(n) O(1) Hard

434 Number of Segments in a String C++ Python O(n) O(1) Easy

443 String Compression C++ Python O(n) O(1) Easy

459 Repeated Substring Pattern C++ Python O(n) O(n) Easy

KMP Algorithm 468 Validate IP Address C++ Python O(1) O(1) Medium

520 Detect Capital C++ Python O(l) O(1) Easy

521 Longest Uncommon Subsequence I C++ Python O(min(a, b)) O(1) Easy

522 Longest Uncommon Subsequence II C++ Python O(l * n^2) O(1) Medium

Sort 524 Longest Word in Dictionary through Deleting C++ Python O((d * l) * logd) O(1) Medium

Sort 527 Word Abbreviation C++ Python O(n * l) ~ O(n^2 * l^2) O(n * l) Hard ?

539 Minimum Time Difference C++ Python O(nlogn) O(n) Medium

541 Reverse String II C++ Python O(n) O(1) Easy

551 Student Attendance Record I C++ Python O(n) O(1) Easy

556 Next Greater Element III C++ Python O(1) O(1) Medium

557 Reverse Words in a String III C++ Python O(n) O(1) Easy

564 Find the Closest Palindrome C++ Python O(l) O(l) Hard

591 Tag Validator C++ Python O(n) O(n) Hard

616 Add Bold Tag in String C++ Python O(n * d * l) O(n) Medium ?

647 Palindromic Substrings C++ Python O(n) O(n) Medium

Manacher's Algorithm 648 Replace Words C++ Python O(n) O(t) Medium

Trie 657 Judge Route Circle C++ Python O(n) O(1) Easy

678 Valid Parenthesis String C++ Python O(n) O(1) Medium

680 Valid Palindrome II C++ Python O(n) O(1) Easy

681 Next Closest Time C++ Python O(1) O(1) Medium

686 Repeated String Match C++ Python O(n + m) O(1) Easy

Rabin-Karp Algorithm 696 Count Binary Substrings C++ Python O(n) O(1) Easy

720 Longest Word in Dictionary C++ Python O(n) O(t) Easy

Trie 722 Remove Comments C++ Python O(n) O(k) Medium

751 IP to CIDR C++ Python O(n) O(1) Medium

758 Bold Words in String C++ Python O(n * l) O(t) Easy ?, variant of Add Bold Tag in String

791 Custom Sort String C++ Python O(n) O(1) Medium

Linked List

# Title Solution Time Space Difficulty Tag Note 002 Add Two Numbers C++ Python O(n) O(1) Medium

021 Merge Two Sorted Lists C++ Python O(n) O(1) Easy

023 Merge k Sorted Lists C++ Python O(nlogk) O(1) Hard

Heap, Divide and Conquer 024 Swap Nodes in Pairs C++ Python O(n) O(1) Easy

025 Reverse Nodes in k-Group C++ Python O(n) O(1) Hard

061 Rotate List C++ Python O(n) O(1) Medium

082 Remove Duplicates from Sorted List II C++ Python O(n) O(1) Medium

083 Remove Duplicates from Sorted List C++ Python O(n) O(1) Easy

092 Reverse Linked List II C++ Python O(n) O(1) Medium

138 Copy List with Random Pointer C++ Python O(n) O(1) Hard

160 Intersection of Two Linked Lists C++ Python O(m + n) O(1) Easy

203 Remove Linked List Elements C++ Python O(n) O(1) Easy

206 Reverse Linked List C++ Python O(n) O(1) Easy

234 Palindrome Linked List C++ Python O(n) O(1) Easy

237 Delete Node in a Linked List C++ Python O(1) O(1) Easy LintCode

328 Odd Even Linked List C++ Python O(n) O(1) Medium

369 Plus One Linked List C++ Python O(n) O(1) Medium ? Two Pointers 445 Add Two Numbers II C++ Python O(m + n) O(m + n) Medium

725 Split Linked List in Parts C++ Python O(n + k) O(1) Medium

Stack

# Title Solution Time Space Difficulty Tag Note 020 Valid Parentheses C++ Python O(n) O(n) Easy

032 Longest Valid Parentheses C++ Python O(n) O(1) Hard

071 Simplify Path C++ Python O(n) O(n) Medium

084 Largest Rectangle in Histogram C++ Python O(n) O(n) Hard

Ascending Stack, DP 085 Maximal Rectangle C++ Python O(m * n) O(n) Hard EPI Ascending Stack 101 Symmetric Tree C++ Python O(n) O(h) Easy

150 Evaluate Reverse Polish Notation C++ Python O(n) O(n) Medium

155 Min Stack C++ Python O(n) O(1) Easy

173 Binary Search Tree Iterator C++ Python O(1) O(h) Medium

224 Basic Calculator C++ Python O(n) O(n) Hard

227 Basic Calculator II C++ Python O(n) O(n) Medium

232 Implement Queue using Stacks C++ Python O(1), amortized O(n) Easy EPI, LintCode

255 Verify Preorder Sequence in Binary Search Tree C++ Python O(n) O(1) Medium ?

272 Closest Binary Search Tree Value II C++ Python O(h + k) O(h) Hard ?

331 Verify Preorder Serialization of a Binary Tree C++ Python O(n) O(1) Medium

341 Flatten Nested List Iterator C++ Python O(n) O(h) Medium ? Iterator 385 Mini Parser C++ Python O(n) O(h) Medium

394 Decode String C++ Python O(n) O(h) Medium

439 Ternary Expression Parser C++ Python O(n) O(1) Medium ?

456 132 Pattern C++ Python O(n) O(n) Medium

636 Exclusive Time of Functions C++ Python O(n) O(n) Medium

682 Baseball Game C++ Python O(n) O(n) Easy

726 Number of Atoms C++ Python O(n) O(n) Hard

735 Asteroid Collision C++ Python O(n) O(n) Medium

736 Parse Lisp Expression C++ Python O(n^2) O(n^2) Hard

739 Daily Temperatures C++ Python O(n) O(n) Medium

770 Basic Calculator IV C++ Python add: O(d * t)
sub: O(d * t)
mul: O(d * t^2)
eval: O(d * t)
to_list: O(d * tlogt) O(e + d * t) Hard

772 Basic Calculator III C++ Python O(n) O(n) Hard

Queue

# Title Solution Time Space Difficulty Tag Note 239 Sliding Window Maximum C++ Python O(n) O(k) Hard EPI, LintCode

281 Zigzag Iterator C++ Python O(n) O(k) Medium ?

346 Moving Average from Data Stream C++ Python O(1) O(w) Easy ?

Heap

# Title Solution Time Space Difficulty Tag Note 264 Ugly Number II C++ Python O(n) O(1) Medium CTCI, LintCode BST, Heap 295 Find Median from Data Stream C++ Python O(nlogn) O(n) Hard EPI, LintCode BST, Heap 313 Super Ugly Number C++ Python O(n * k) O(n + k) Medium

BST, Heap 358 Rearrange String k Distance Apart C++ Python O(n) O(n) Hard ? Greedy, Heap 373 Find K Pairs with Smallest Sums C++ Python O(k * log(min(n, m, k))) O(min(n, m, k)) Medium

378 Kth Smallest Element in a Sorted Matrix C++ Python O(k * log(min(n, m, k))) O(min(n, m, k)) Medium LintCode

407 Trapping Rain Water II C++ Python O(m * n * (logm + logn)) O(m * n) Hard LintCode

632 Smallest Range C++ Python O(nlogk) O(k) Hard

Tree

# Title Solution Time Space Difficulty Tag Note 094 Binary Tree Inorder Traversal C++ Python O(n) O(1) Medium

Morris Traversal 099 Recover Binary Search Tree C++ Python O(n) O(1) Hard

Morris Traversal 144 Binary Tree Preorder Traversal C++ Python O(n) O(1) Medium

Morris Traversal 145 Binary Tree Postorder Traversal C++ Python O(n) O(1) Hard

Morris Traversal 208 Implement Trie (Prefix Tree) C++ Python O(n) O(1) Medium

Trie 211 Add and Search Word - Data structure design C++ Python O(min(n, h)) O(min(n, h)) Medium

Trie, DFS 226 Invert Binary Tree C++ Python O(n) O(h), O(w) Easy

297 Serialize and Deserialize Binary Tree C++ Python O(n) O(h) Hard LintCode DFS 307 Range Sum Query - Mutable C++ Python ctor: O(n), update: O(logn), query: O(logn) O(n) Medium LintCode DFS, Segment Tree, BIT 308 Range Sum Query 2D - Mutable C++ Python ctor: O(m * n), update: O(logm + logn), query: O(logm + logn) O(m * n) Hard ? DFS, Segment Tree, BIT 315 Count of Smaller Numbers After Self C++ Python O(nlogn) O(n) Hard LintCode BST, BIT, Divide and Conquer 525 Contiguous Array C++ Python O(n) O(n) Medium

529 Minesweeper C++ Python O(m * n) O(m + n) Medium

536 Construct Binary Tree from String C++ Python O(n) O(h) Medium ?

538 Convert BST to Greater Tree C++ Python O(n) O(h) Easy

543 Diameter of Binary Tree C++ Python O(n) O(h) Easy

545 Boundary of Binary Tree C++ Python O(n) O(h) Medium ?

548 Split Array with Equal Sum C++ Python O(n^2) O(n) Medium ?

563 Binary Tree Tilt C++ Python O(n) O(n) Easy

572 Subtree of Another Tree C++ Python O(m * n) O(h) Easy

606 Construct String from Binary Tree C++ Python O(n) O(h) Easy

617 Merge Two Binary Trees C++ Python O(n) O(h) Easy

623 Add One Row to Tree C++ Python O(n) O(h) Medium

637 Average of Levels in Binary Tree C++ Python O(n) O(h) Easy

652 Find Duplicate Subtrees C++ Python O(n) O(n) Medium

DFS, Hash 653 Two Sum IV - Input is a BST C++ Python O(n) O(h) Easy

Two Pointers 654 Maximum Binary Tree C++ Python O(n) O(n) Medium LintCode Descending Stack 655 Print Binary Tree C++ Python O(n) O(h) Medium

662 Maximum Width of Binary Tree C++ Python O(n) O(h) Medium

DFS 663 Equal Tree Partition C++ Python O(n) O(n) Medium ? Hash 677 Map Sum Pairs C++ Python O(n) O(t) Medium

Trie 684 Redundant Connection C++ Python O(n) O(n) Medium

Union Find 685 Redundant Connection II C++ Python O(n) O(n) Hard

Union Find 687 Longest Univalue Path C++ Python O(n) O(h) Easy

699 Falling Squares C++ Python O(nlogn) O(n) Hard

Segment Tree

Hash Table

# Title Solution Time Space Difficulty Tag Note 001 Two Sum C++ Python O(n) O(n) Easy

003 Longest Substring Without Repeating Characters C++ Python O(n) O(1) Medium

030 Substring with Concatenation of All Words C++ Python O((m + n) * k) O(n * k) Hard

036 Valid Sudoku C++ Python O(9^2) O(9) Easy

049 Group Anagrams C++ Python O(n * glogg) O(n) Medium

076 Minimum Window Substring C++ Python O(n) O(k) Hard

149 Max Points on a Line C++ Python O(n^2) O(n) Hard

159 Longest Substring with At Most Two Distinct Characters C++ Python O(n) O(1) Hard ?

170 Two Sum III - Data structure design C++ Python O(n) O(n) Easy ?

187 Repeated DNA Sequences Python O(n) O(n) Medium

202 Happy Number C++ Python O(k) O(k) Easy

204 Count Primes C++ Python O(n) O(n) Easy

205 Isomorphic Strings C++ Python O(n) O(1) Easy

217 Contains Duplicate C++ Python O(n) O(n) Easy

219 Contains Duplicate II C++ Python O(n) O(n) Easy

244 Shortest Word Distance II C++ Python ctor: O(n), lookup: O(a + b) O(n) Medium ?

246 Strobogrammatic Number C++ Python O(n) O(1) Easy ?

249 Group Shifted Strings C++ Python O(nlogn) O(n) Easy ?

266 Palindrome Permutation C++ Python O(n) O(1) Easy ?

288 Unique Word Abbreviation C++ Python ctor: O(n), lookup: O(1) O(k) Easy ?

290 Word Pattern C++ Python O(n) O(c) Easy variant of Isomorphic Strings

299 Bulls and Cows C++ Python O(n) O(1) Easy

305 Number of Islands II C++ Python O(k) O(k) Hard LintCode, ? Union Find 314 Binary Tree Vertical Order Traversal C++ Python O(n) O(n) Medium ? BFS 323 Number of Connected Components in an Undirected Graph C++ Python O(n) O(n) Medium ? Union Find 325 Maximum Size Subarray Sum Equals k C++ Python O(n) O(n) Medium ?

336 Palindrome Pairs C++ Python O(n * k^2) O(n * k) Hard

340 Longest Substring with At Most K Distinct Characters C++ Python O(n) O(1) Hard ?

356 Line Reflection C++ Python O(n) O(n) Medium ? Hash, Two Pointers 387 First Unique Character in a String C++ Python O(n) O(n) Easy

388 Longest Absolute File Path C++ Python O(n) O(d) Medium

Stack 409 Longest Palindrome C++ Python O(n) O(1) Easy

424 Longest Repeating Character Replacement C++ Python O(n) O(1) Medium

438 Find All Anagrams in a String C++ Python O(n) O(1) Easy

447 Number of Boomerangs C++ Python O(n^2) O(n) Easy

454 4Sum II C++ Python O(n^2) O(n^2) Medium

473 Matchsticks to Square C++ Python O(n * s * 2^n) O(n * (2^n + s)) Medium

523 Continuous Subarray Sum C++ Python O(n) O(k) Medium

532 K-diff Pairs in an Array C++ Python O(n) O(n) Easy

554 Brick Wall C++ Python O(n) O(m) Medium

560 Subarray Sum Equals K C++ Python O(n) O(n) Medium

561 Array Partition I C++ Python O(r) O(r) Easy

575 Distribute Candies C++ Python O(n) O(n) Easy

594 Longest Harmonious Subsequence C++ Python O(n) O(n) Easy

599 Minimum Index Sum of Two Lists C++ Python O((m + n) * l) O(m * l) Easy

609 Find Duplicate File in System C++ Python O(n * l) O(n * l) Medium

721 Accounts Merge C++ Python O(nlogn) O(n) Medium

Union Find 734 Sentence Similarity C++ Python O(n + p) O(p) Easy

737 Sentence Similarity II C++ Python O(n + p) O(p) Medium

Union Find 748 Shortest Completing Word C++ Python O(n) O(1) Easy

760 Find Anagram Mappings C++ Python O(n) O(n) Easy

771 Jewels and Stones C++ Python O(m + n) O(n) Easy

Math

# Title Solution Time Space Difficulty Tag Note 007 Reverse Integer C++ Python O(1) O(1) Easy

009 Palindrome Number C++ Python O(1) O(1) Easy

012 Integer to Roman C++ Python O(n) O(1) Medium

013 Roman to Integer C++ Python O(n) O(1) Easy

029 Divide Two Integers C++ Python O(1) O(1) Medium

050 Pow(x, n) C++ Python O(1) O(1) Medium

060 Permutation Sequence C++ Python O(n^2) O(n) Medium

Cantor Ordering 065 Valid Number C++ Python O(n) O(1) Hard

Automata 089 Gray Code C++ Python O(2^n) O(1) Medium

166 Fraction to Recurring Decimal C++ Python O(logn) O(1) Medium

168 Excel Sheet Column Title C++ Python O(logn) O(1) Easy

171 Excel Sheet Column Number C++ Python O(n) O(1) Easy

172 Factorial Trailing Zeroes C++ Python O(1) O(1) Easy

223 Rectangle Area C++ Python O(1) O(1) Easy

233 Number of Digit One C++ Python O(1) O(1) Hard CTCI, LintCode

248 Strobogrammatic Number III C++ Python O(5^(n/2)) O(n) Hard ?

258 Add Digits C++ Python O(1) O(1) Easy

263 Ugly Number C++ Python O(1) O(1) Easy

292 Nim Game C++ Python O(1) O(1) Easy LintCode

319 Bulb Switcher C++ Python O(1) O(1) Medium

326 Power of Three C++ Python O(1) O(1) Easy

335 Self Crossing C++ Python O(n) O(1) Hard

338 Counting Bits C++ Python O(n) O(n) Medium

343 Integer Break C++ Python O(logn) O(1) Medium

Tricky, DP 365 Water and Jug Problem C++ Python O(logn) O(1) Medium

Bézout's identity 372 Super Pow C++ Python O(n) O(1) Medium

382 Linked List Random Node C++ Python O(n) O(1) Medium

Reservoir Sampling 386 Lexicographical Numbers C++ Python O(n) O(1) Medium

390 Elimination Game C++ Python O(logn) O(1) Medium

391 Perfect Rectangle C++ Python O(n) O(n) Hard

398 Random Pick Index C++ Python O(n) O(1) Medium

Reservoir Sampling 400 Nth Digit C++ Python O(logn) O(1) Easy

413 Arithmetic Slices C++ Python O(n) O(1) Medium

423 Reconstruct Original Digits from English C++ Python O(n) O(1) Medium GCJ2016 - Round 1B

441 Arranging Coins C++ Python O(nlogn) O(1) Easy

Binary Search 453 Minimum Moves to Equal Array Elements C++ Python O(n) O(1) Easy

458 Poor Pigs C++ Python O(n) O(1) Easy

469 Convex Polygon C++ Python O(n) O(1) Medium ?

537 Complex Number Multiplication C++ Python O(1) O(1) Medium

553 Optimal Division C++ Python O(n) O(1) Medium

573 Squirrel Simulation C++ Python O(n) O(1) Medium ?

592 Fraction Addition and Subtraction C++ Python O(nlogx) O(n) Medium

593 Valid Square C++ Python O(1) O(1) Medium

598 Range Addition II C++ Python O(p) O(1) Easy

625 Minimum Factorization C++ Python O(loga) O(1) Medium ?

628 Maximum Product of Three Numbers C++ Python O(n) O(1) Easy

633 Sum of Square Numbers C++ Python O(sqrt(c) * logc) O(1) Easy

634 Find the Derangement of An Array C++ Python O(n) O(1) Medium ?

640 Solve the Equation C++ Python O(n) O(n) Medium

651 4 Keys Keyboard C++ Python O(1) O(1) Medium ? Math, DP 660 Remove 9 C++ Python O(logn) O(1) Hard ?

672 Bulb Switcher II C++ Python O(1) O(1) Medium

728 Self Dividing Numbers C++ Python O(n) O(1) Medium

754 Reach a Number C++ Python O(logn) O(1) Medium

775 Global and Local Inversions C++ Python O(n) O(1) Medium

779 K-th Symbol in Grammar C++ Python O(1) O(1) Medium

780 Reaching Points C++ Python O(log(max(m, n))) O(1) Hard

781 Rabbits in Forest C++ Python O(n) O(n) Medium

782 Transform to Chessboard C++ Python O(n^2) O(n) Hard

789 Escape The Ghosts C++ Python O(n) O(1) Medium

Sort

# Title Solution Time Space Difficulty Tag Note 056 Merge Intervals C++ Python O(nlogn) O(1) Hard

057 Insert Interval C++ Python O(n) O(1) Hard

075 Sort Colors C++ Python O(n) O(1) Medium

Tri Partition 088 Merge Sorted Array C++ Python O(n) O(1) Easy

147 Insertion Sort List C++ Python O(n^2) O(1) Medium

148 Sort List C++ Python O(nlogn) O(logn) Medium

164 Maximum Gap C++ Python O(n) O(n) Hard

Tricky 179 Largest Number C++ Python O(nlogn) O(1) Medium

218 The Skyline Problem C++ Python O(nlogn) O(n) Hard

Sort, BST 252 Meeting Rooms C++ Python O(nlogn) O(n) Easy ?

253 Meeting Rooms II C++ Python O(nlogn) O(n) Medium ?

274 H-Index C++ Python O(n) O(n) Medium

Counting Sort 280 Wiggle Sort C++ Python O(n) O(1) Medium ?

324 Wiggle Sort II C++ Python O(n) on average O(1) Medium variant of Sort Colors Tri Partition 347 Top K Frequent Elements C++ Python O(n) O(n) Medium

Quick Select, Heap, Bucket Sort 406 Queue Reconstruction by Height C++ Python O(n * sqrt(n)) O(n) Medium

Tricky 451 Sort Characters By Frequency C++ Python O(n) O(n) Medium

692 Top K Frequent Words C++ Python O(n + klogk) on average O(n) Medium

Quick Select, Heap, Bucket Sort

Two Pointers

# Title Solution Time Space Difficulty Tag Note 019 Remove Nth Node From End of List C++ Python O(n) O(1) Easy

086 Partition List C++ Python O(n) O(1) Medium

141 Linked List Cycle C++ Python O(n) O(1) Easy

142 Linked List Cycle II C++ Python O(n) O(1) Medium

143 Reorder List C++ Python O(n) O(1) Medium

167 Two Sum II - Input array is sorted C++ Python O(n) O(1) Medium

259 3Sum Smaller C++ Python O(n^2) O(1) Medium ?, LintCode

283 Move Zeroes C++ Python O(n) O(1) Easy

287 Find the Duplicate Number C++ Python O(n) O(1) Hard

Binary Search, Two Pointers 344 Reverse String C++ Python O(n) O(1) Easy

345 Reverse Vowels of a String C++ Python O(n) O(1) Easy

349 Intersection of Two Arrays C++ Python O(m + n) O(min(m, n)) Easy EPI Hash, Binary Search 350 Intersection of Two Arrays II C++ Python O(m + n) O(1) Easy EPI Hash, Binary Search 360 Sort Transformed Array C++ Python O(n) O(1) Medium ?

457 Circular Array Loop C++ Python O(n) O(1) Medium

567 Permutation in String C++ Python O(n) O(1) Medium

611 Valid Triangle Number C++ Python O(n^2) O(1) Medium

777 Swap Adjacent in LR String C++ Python O(n) O(1) Medium

Recursion

# Title Solution Time Space Difficulty Tag Note 095 Unique Binary Search Trees II C++ Python O(4^n / n^(3/2) O(4^n / n^(3/2) Medium

098 Validate Binary Search Tree C++ Python O(n) O(1) Medium

100 Same Tree C+ Python O(n) O(h) Easy

104 Maximum Depth of Binary Tree C++ Python O(n) O(h) Easy

105 Construct Binary Tree from Preorder and Inorder Traversal C++ Python O(n) O(n) Medium

106 Construct Binary Tree from Inorder and Postorder Traversal C++ Python O(n) O(n) Medium

108 Convert Sorted Array to Binary Search Tree C++ Python O(n) O(logn) Medium

109 Convert Sorted List to Binary Search Tree C++ Python O(n) O(logn) Medium

110 Balanced Binary Tree Python O(n) O(h) Easy

111 Minimum Depth of Binary Tree Python O(n) O(h) Easy

114 Flatten Binary Tree to Linked List Python O(n) O(h) Medium

116 Populating Next Right Pointers in Each Node Python O(n) O(1) Medium

124 Binary Tree Maximum Path Sum Python O(n) O(h) Hard

129 Sum Root to Leaf Numbers Python O(n) O(h) Medium

156 Binary Tree Upside Down Python O(n) O(1) Medium ?

241 Different Ways to Add Parentheses C++ Python O(n * 4^n / n^(3/2)) O(n * 4^n / n^(3/2)) Medium

298 Binary Tree Longest Consecutive Sequence C++ Python O(n) O(h) Medium ?

327 Count of Range Sum C++ Python O(nlogn) O(n) Hard

333 Largest BST Subtree C++ Python O(n) O(h) Medium ?

337 House Robber III C++ Python O(n) O(h) Medium

395 Longest Substring with At Least K Repeating Characters C++ Python O(n) O(1) Medium

404 Sum of Left Leaves C++ Python O(n) O(h) Easy

437 Path Sum III C++ Python O(n) O(h) Easy

544 Output Contest Matches C++ Python O(n) O(n) Medium

549 Binary Tree Longest Consecutive Sequence II C++ Python O(n) O(h) Medium ?

669 Trim a Binary Search Tree C++ Python O(n) O(h) Easy

671 Second Minimum Node In a Binary Tree C++ Python O(n) O(h) Easy

761 Special Binary String C++ Python O(n^2) O(n) Hard

Binary Search

# Title Solution Time Space Difficulty Tag Note 004 Median of Two Sorted Arrays C++ Python O(log(min(m, n))) O(1) Hard

033 Search in Rotated Sorted Array C++ Python O(logn) O(1) Hard

034 Search for a Range C++ Python O(logn) O(1) Medium

305 Search Insert Position C++ Python O(logn) O(1) Medium

069 Sqrt(x) C++ Python O(logn) O(1) Medium

074 Search a 2D Matrix C++ Python O(logm + logn) O(1) Medium

081 Search in Rotated Sorted Array II C++ Python O(logn) O(1) Medium

153 Find Minimum in Rotated Sorted Array C++ Python O(logn) O(1) Medium

154 Find Minimum in Rotated Sorted Array II C++ Python O(logn) ~ O(n) O(1) Hard

162 Find Peak Element C++ Python O(logn) O(1) Medium

222 Count Complete Tree Nodes C++ Python O((logn)^2) O(1) Medium

275 H-Index II C++ Python O(logn) O(1) Medium

Binary Search 278 First Bad Version C++ Python O(logn) O(1) Easy LintCode

300 Longest Increasing Subsequence C++ Python O(nlogn) O(n) Medium CTCI, LintCode Binary Search, DP 302 Smallest Rectangle Enclosing Black Pixels C++ Python O(nlogn) O(1) Hard ?

354 Russian Doll Envelopes C++ Python O(nlogn) O(1) Hard

363 Max Sum of Rectangle No Larger Than K C++ Python O(min(m, n)^2 * max(m, n) * logn(max(m, n))) O(max(m, n)) Hard

367 Valid Perfect Square C++ Python O(logn) O(1) Medium

374 Guess Number Higher or Lower C++ Python O(logn) O(1) Easy

410 Split Array Largest Sum C++ Python O(nlogs) O(1) Hard

436 Find Right Interval C++ Python O(nlogn) O(n) Medium

475 Heaters C++ Python O((m + n) * logn) O(1) Easy

540 Single Element in a Sorted Array C++ Python O(logn) O(1) Medium

658 Find K Closest Elements C++ Python O(logn + k) O(1) Medium

668 Kth Smallest Number in Multiplication Table C++ Python O(m * log(m * n)) O(1) Hard

719 Find K-th Smallest Pair Distance C++ Python O(nlogn + nlogw) O(1) Hard

744 Find Smallest Letter Greater Than Target C++ Python O(logn) O(1) Easy

774 Minimize Max Distance to Gas Station C++ Python O(nlogr) O(1) Hard

786 K-th Smallest Prime Fraction C++ Python O(nlogr) O(1) Hard

793 Preimage Size of Factorial Zeroes Function C++ Python O((logn)^2) O(1) Hard

Binary Search Tree

# Title Solution Time Space Difficulty Tag Note 220 Contains Duplicate III C++ Python O(nlogk) O(k) Medium

230 Kth Smallest Element in a BST C++ Python O(max(h, k)) O(min(h, k)) Medium

235 Lowest Common Ancestor of a Binary Search Tree C++ Python O(h) O(1) Easy EPI

270 Closest Binary Search Tree Value C++ Python O(h) O(1) Easy ?

285 Inorder Successor in BST C++ Python O(h) O(1) Medium ?

352 Data Stream as Disjoint Intervals C++ Python O(logn) O(n) Hard

449 Serialize and Deserialize BST C++ Python O(n) O(h) Medium

450 Delete Node in a BST C++ Python O(h) O(h) Medium

530 Minimum Absolute Difference in BST C++ Python O(n) O(h) Easy

776 Split BST C++ Python O(n) O(h) Medium ?

783 Minimum Distance Between BST Nodes C++ Python O(n) O(h) Easy

Breadth-First Search

# Title Solution Time Space Difficulty Tag Note 102 Binary Tree Level Order Traversal C++ Python O(n) O(n) Easy

107 Binary Tree Level Order Traversal II Python O(n) O(n) Easy

103 Binary Tree Zigzag Level Order Traversal Python O(n) O(n) Medium

117 Populating Next Right Pointers in Each Node II Python O(n) O(1) Hard

127 Word Ladder Python O(n * d) O(d) Medium

130 Surrounded Regions C++ Python O(m * n) O(m + n) Medium

133 Clone Graph Python O(n) O(n) Medium

207 Course Schedule Python O(|V| + |E|) O(|E|) Medium

Topological Sort 210 Course Schedule II Python O(|V| + |E|) O(|E|) Medium

Topological Sort 261 Graph Valid Tree C++ Python O(|V| + |E|) O(|V| + |E|) Medium ?

269 Alien Dictionary C++ Python O(n) O(1) Hard ? Topological Sort, BFS, DFS 286 Walls and Gates C++ Python O(m * n) O(g) Medium ?

310 Minimum Height Trees C++ Python O(n) O(n) Medium

317 Shortest Distance from All Buildings C++ Python O(k * m * n) O(m * n) Hard ?

433 Minimum Genetic Mutation C++ Python O(n * b) O(b) Medium

444 Sequence Reconstruction C++ Python O(n * s) O(n) Medium ? Topological Sort 542 01 Matrix C++ Python O(m * n) O(m * n) Medium

DP 666 Path Sum IV C++ Python O(n) O(w) Medium ? Topological Sort 675 Cut Off Trees for Golf Event C++ Python O(t * m * n) O(m * n) Hard

A* Search Algorithm 742 Closest Leaf in a Binary Tree C++ Python O(n) O(n) Medium

743 Network Delay Time C++ Python O(|E| + |V|log|V|) O(|E| + |V|) Medium

Dijkstra's algorithm 752 Open the Lock C++ Python O(k * n^k + d) O(k * n^k + d) Medium

773 Sliding Puzzle C++ Python O((m * n) * (m * n)!) O((m * n) * (m * n)!) Hard

A* Search Algorithm 787 Cheapest Flights Within K Stops C++ Python O(|E| + |V|log|V|) O(|E| + |V|) Medium

Dijkstra's algorithm

Depth-First Search

# Title Solution Time Space Difficulty Tag Note 112 Path Sum Python O(n) O(h) Easy

113 Path Sum II Python O(n) O(h) Medium

199 Binary Tree Right Side View Python O(n) O(h) Medium

200 Number of Islands Python O(m * n) O(m * n) Medium

236 Lowest Common Ancestor of a Binary Tree C++ Python O(n) O(h) Medium EPI

247 Strobogrammatic Number II C++ Python O(n^2 * 5^(n/2)) O(n) Medium ?

250 Count Univalue Subtrees C++ Python O(n) O(h) Medium ?

257 Binary Tree Paths C++ Python O(n * h) O(h) Easy

282 Expression Add Operators C++ Python O(4^n) O(n) Hard

301 Remove Invalid Parentheses C++ Python O(C(n, c)) O(c) Hard

329 Longest Increasing Path in a Matrix C++ Python O(m * n) O(m * n) Hard

332 Reconstruct Itinerary C++ Python O(t! / (n1! * n2! * ... nk!)) O(t) Medium

339 Nested List Weight Sum C++ Python O(n) O(h) Easy ?

364 Nested List Weight Sum II C++ Python O(n) O(h) Medium ?

366 Find Leaves of Binary Tree C++ Python O(n) O(h) Medium ?

399 Evaluate Division C++ Python O(q * |V|!) O(e) Medium

417 Pacific Atlantic Water Flow C++ Python O(m * n) O(m * n) Medium

440 K-th Smallest in Lexicographical Order C++ Python O(logn) O(logn) Hard

464 Can I Win C++ Python O(n!) O(n) Medium

547 Friend Circles C++ Python O(n^2) O(n) Medium

Union Find 582 Kill Process C++ Python O(n) O(n) Medium ? DFS, BFS 638 Shopping Offers C++ Python O(n * 2^n) O(n) Medium

690 Employee Importance C++ Python O(n) O(h) Easy

DFS, BFS 694 Number of Distinct Islands C++ Python O(m * n) O(m * n) Medium ?

695 Max Area of Island C++ Python O(m * n) O(m * n) Easy

711 Number of Distinct Islands II C++ Python O((m * n) * log(m * n)) O(m * n) Hard ? Hash 733 Max Area of Island C++ Python O(m * n) O(m * n) Easy

749 Contain Virus C++ Python O((m * n)^(4/3)) O(m * n) Hard

Simulation 753 Cracking the Safe C++ Python O(k^n) O(k^n) Hard

de Bruijn sequences, Lyndon word 756 Pyramid Transition Matrix C++ Python O(a^b) O(a^b) Medium

785 Is Graph Bipartite? C++ Python O(|V| + |E|) O(|V|) Medium

Backtracking

# Title Solution Time Space Difficulty Tag Note 017 Letter Combinations of a Phone Number Python O(n * 4^n) O(n) Medium

022 Generate Parentheses Python O(4^n / n^(3/2)) O(n) Medium

037 Sudoku Solver Python O((9!)^9) O(1) Hard

039 Combination Sum Python O(k * n^k) O(k) Medium

040 Combination Sum II Python O(k * C(n, k)) O(k) Medium

046 Permutations Python O(n * n!) O(n) Medium

047 Permutations II Python O(n * n!) O(n) Medium

051 N-Queens Python O(n!) O(n) Hard

052 N-Queens-II Python O(n!) O(n) Hard

077 Combinations Python O(O(k * C(n, k))) O(k) Medium

079 Word Search Python O(m * n * l) O(l) Medium

093 Restore IP Addresses Python O(1) O(1) Medium

078 Subsets C++ Python O(n * 2^n) O(1) Medium

090 Subsets II C++ Python O(n * 2^n) O(1) Medium

126 Word Ladder II Python O(n * d) O(d) Hard

131 Palindrome Partitioning Python O(n^2) ~ O(2^n) O(n^2) Medium

140 Word Break II C++ Python O(n * l^2 + n * r) O(n^2) Hard

212 Word Search II C++ Python O(m * n * l) O(l) Hard LintCode Trie, DFS 216 Combination Sum III C++ Python O(k * C(n, k)) O(k) Medium

254 Factor Combinations C++ Python O(nlogn) O(logn) Medium ?

267 Palindrome Permutation II C++ Python O(n * n!) O(n) Medium ?

291 Word Pattern II C++ Python O(n * C(n - 1, c - 1)) O(n + c) Hard ?

294 Flip Game II C++ Python O(n + c^2) O(c) Medium ? DP, Hash 320 Generalized Abbreviation C++ Python O(n * 2^n) O(n) Medium ?

425 Word Squares C++ Python O(n^2 * n!) O(n^2) Hard ?

526 Beautiful Arrangement C++ Python O(n!) O(n) Medium

676 Implement Magic Dictionary C++ Python O(n) O(d) Medium

Trie, DFS 679 24 Game C++ Python O(1) O(1) Hard

DFS 698 Partition to K Equal Sum Subsets C++ Python O(n * 2^n) O(2^n) Medium

DFS, DP, Memoization 718 Maximum Length of Repeated Subarray C++ Python O(m * n) O(min(m, n)) Medium

DP, Hash, Binary Search 784 Letter Case Permutation C++ Python O(n * 2^n) O(1) Easy

Dynamic Programming

# Title Solution Time Space Difficulty Tag Note 010 Regular Expression Matching Python O(m * n) O(n) Hard

053 Maximum Subarray Python O(n) O(1) Medium

062 Unique Paths Python O(m * n) O(m + n) Medium

063 Unique Paths II Python O(m * n) O(m + n) Medium

064 Minimum Path Sum Python O(m * n) O(m + n) Medium

070 Climbing Stairs Python O(n) O(1) Easy

072 Edit Distance Python O(m * n) O(m + n) Hard

087 Scramble String Python O(n^4) O(n^3) Hard

091 Decode Ways C++ Python O(n) O(1) Medium

096 Unique Binary Search Trees Python O(n) O(1) Medium

Math 097 Interleaving String Python O(m * n) O(m + n) Hard

115 Distinct Subsequences Python O(n^2) O(n) Hard

120 Triangle Python O(m * n) O(n) Medium

123 Best Time to Buy and Sell Stock III Python O(n) O(1) Hard

132 Palindrome Partitioning II Python O(n^2) O(n^2) Hard

139 Word Break C++ Python O(n * l^2) O(n) Medium

152 Maximum Product Subarray Python O(n) O(1) Medium

174 Dungeon Game Python O(m * n) O(m + n) Hard

188 Best Time to Buy and Sell Stock IV Python O(k * n) O(k) Hard

198 House Robber Python O(n) O(1) Easy

213 House Robber II C++ Python O(n) O(1) Medium

221 Maximal Square C++ Python O(n^2) O(n) Medium EPI

256 Paint House C++ Python O(n) O(1) Medium ?

265 Paint House II C++ Python O(n * k) O(k) Hard ?

276 Paint Fence C++ Python O(n) O(1) Easy ?

279 Perfect Squares C++ Python O(n * sqrt(n)) O(n) Medium

Hash 303 Range Sum Query - Immutable C++ Python ctor: O(n), lookup: O(1) O(n) Easy

304 Range Sum Query 2D - Immutable C++ Python ctor: O(m * n), lookup: O(1) O(m * n) Medium

309 Best Time to Buy and Sell Stock with Cooldown C++ Python O(n) O(1) Medium

312 Burst Balloons C++ Python O(n^3) O(n^2) Hard

322 Coin Change C++ Python O(n * k) O(k) Medium

351 Android Unlock Patterns C++ Python O(9^2 * 2^9) O(9 * 2^9) Medium ? Backtracking 357 Count Numbers with Unique Digits C++ Python O(n) O(1) Medium

Backtracking, Math 361 Bomb Enemy C++ Python O(m * n) O(m * n) Medium ?

368 Largest Divisible Subset C++ Python O(n^2) O(n) Medium

375 Guess Number Higher or Lower II C++ Python O(n^2) O(n^2) Medium

377 Combination Sum IV C++ Python O(nlogn + n * t) O(t) Medium

403 Frog Jump C++ Python O(n) O(n) ~ O(n^2) Hard

416 Partition Equal Subset Sum C++ Python O(n * s) O(s) Medium

418 Sentence Screen Fitting C++ Python O(r + n * c) O(n) Medium ?

446 Arithmetic Slices II - Subsequence C++ Python O(n^2) O(n * d) Hard

465 Optimal Account Balancing C++ Python O(n * 2^n) O(n * 2^n) Hard ?

466 Count The Repetitions C++ Python O(s1 * min(s2, n1)) O(s2) Hard

467 Unique Substrings in Wraparound String C++ Python O(n) O(1) Medium

471 Encode String with Shortest Length C++ Python O(n^3) on average O(n^2) Medium ?

472 Concatenated Words C++ Python O(n * l^2) O(n * l) Medium

474 Ones and Zeroes C++ Python O(s * m * n) O(m * n) Medium

546 Remove Boxes C++ Python O(n^3) ~ O(n^4) O(n^3) Hard

552 Student Attendance Record II C++ Python O(n) O(1) Hard

562 Longest Line of Consecutive One in Matrix C++ Python O(m * n) O(n) Medium ?

568 Maximum Vacation Days C++ Python O(n^2 * k) O(k) Hard ?

576 Out of Boundary Paths C++ Python O(N * m * n) O(m * n) Medium

583 Delete Operation for Two Strings C++ Python O(m * n) O(n) Medium

600 Non-negative Integers without Consecutive Ones C++ Python O(1) O(1) Hard

629 K Inverse Pairs Array C++ Python O(n * k) O(k) Hard

639 Decode Ways II C++ Python O(n) O(1) Hard

650 2 Keys Keyboard C++ Python O(sqrt(n)) O(1) Medium

656 Coin Path C++ Python O(n * B) O(n) Hard ?

664 Strange Printer C++ Python O(n^3) O(n^2) Hard

673 Number of Longest Increasing Subsequence C++ Python O(n^2) O(n) Medium

688 Knight Probability in Chessboard C++ Python O(k * n^2) O(n^2) Medium

689 Maximum Sum of 3 Non-Overlapping Subarrays C++ Python O(n) O(n) Hard

691 Stickers to Spell Word C++ Python O(T * S^T) O(T * S^T) Hard

Backtracking, Memoization 712 Minimum ASCII Delete Sum for Two Strings C++ Python O(m * n) O(n) Medium

714 Best Time to Buy and Sell Stock with Transaction Fee C++ Python O(n) O(1) Medium

727 Minimum Window Subsequence C++ Python O(s * t) O(s) Hard ?

730 Count Different Palindromic Subsequences C++ Python O(n^2) O(n) Hard

740 Delete and Earn C++ Python O(n) O(1) Medium

741 Cherry Pickup C++ Python O(n^3) O(n^2) Hard

746 Min Cost Climbing Stairs C++ Python O(n) O(1) Easy

750 Number Of Corner Rectangles C++ Python O(n * m^2) O(n * m) Medium

764 Largest Plus Sign C++ Python O(n^2) O(n^2) Medium

788 Rotated Digits C++ Python O(logn) O(logn) Easy

Memoization 790 Domino and Tromino Tiling C++ Python O(logn) O(logn) Medium

Matrix Exponentiation

Greedy

# Title Solution Time Space Difficulty Tag Note 011 Container With Most Water C++ Python O(n) O(1) Medium

042 Trapping Rain Water C++ Python O(n) O(1) Hard

Tricky 044 Wildcard Matching Python O(m + n) O(1) Hard

Tricky 045 Jump Game II Python O(n) O(1) Hard

055 Jump Game Python O(n) O(1) Medium

122 Best Time to Buy and Sell Stock II Python O(n) O(1) Easy

134 Gas Station Python O(n) O(1) Medium

135 Candy C++ Python O(n) O(n) Hard

316 Remove Duplicate Letters C++ Python O(n) O(k) Hard

Ascending Stack 321 Create Maximum Number C++ Python O(k * (m + n + k)) ~ O(k * (m + n + k^2)) O(m + n + k^2) Hard variant of Delete Digits Greedy, DP 330 Patching Array C++ Python O(s + logn) O(1) Hard

376 Wiggle Subsequence C++ Python O(n) O(1) Medium

392 Is Subsequence C++ Python O(n) O(1) Medium

397 Integer Replacement C++ Python O(n) O(1) Medium

Math 402 Remove K Digits C++ Python O(n) O(n) Medium LintCode

435 Non-overlapping Intervals C++ Python O(nlogn) O(1) Medium

Scan Line 452 Minimum Number of Arrows to Burst Balloons C++ Python O(nlogn) O(1) Medium

455 Assign Cookies C++ Python O(nlogn) O(1) Easy

621 Task Scheduler C++ Python O(n) O(1) Medium

630 Course Schedule III C++ Python O(nlogn) O(k) Hard

646 Maximum Length of Pair Chain C++ Python O(nlogn) O(1) Medium similar to Non-overlapping Intervals Scan Line 649 Dota2 Senate C++ Python O(n) O(n) Medium

659 Split Array into Consecutive Subsequences C++ Python O(n) O(1) Medium

738 Monotone Increasing Digits C++ Python O(1) O(1) Medium

757 Set Intersection Size At Least Two C++ Python O(nlogn) O(n) Hard

759 Employee Free Time C++ Python O(m * logn) O(n) Hard

763 Partition Labels C++ Python O(n) O(n) Medium

767 Reorganize String C++ Python O(n) O(1) Medium

Graph

# Title Solution Time Space Difficulty Tag Note 765 Couples Holding Hands C++ Python O(n) O(n) Hard

Geometry

# Title Solution Time Space Difficulty Tag Note 587 Erect the Fence C++ Python O(nlogn) O(n) Hard

Monotone Chain

Design

# Title Solution Time Space Difficulty Tag Note 146 LRU Cache C++ Python O(1) O(k) Hard

225 Implement Stack using Queues C++ Python push: O(n), pop: O(1), top: O(1) O(n) Easy

284 Peeking Iterator C++ Python O(1) O(1) Medium

348 Design Tic-Tac-Toe C++ Python O(1) O(n^2) Medium ?

353 Design Snake Game C++ Python O(1) O(s) Medium ? Deque 355 Design Twitter C++ Python O(klogu) O(t + f) Medium LintCode Heap 359 Logger Rate Limiter C++ Python O(1), amortized O(k) Easy ? Deque 362 Design Hit Counter C++ Python O(1), amortized O(k) Medium ? Deque 379 Design Phone Directory C++ Python O(1) O(n) Medium ?

380 Insert Delete GetRandom O(1) C++ Python O(1) O(n) Hard

381 Insert Delete GetRandom O(1) - Duplicates allowed C++ Python O(1) O(n) Hard

432 All O`one Data Structure C++ Python O(1) O(n) Hard

460 LFU Cache C++ Python O(1) O(k) Hard

535 Encode and Decode TinyURL C++ Python O(1) O(n) Medium

588 Design In-Memory File System C++ Python ls: O(l + klogk)
mkdir: O(l)
addContentToFile: O(l + c)
readContentFromFile: O(l + c) O(n + s) Hard ?

604 Design Compressed String Iterator C++ Python O(1) O(1) Easy ?

631 Design Excel Sum Formula C++ Python set: O((r * c)^2)
get: O(1)
sum: O((r * c)^2) O(r * c) Hard ?

635 Design Log Storage System C++ Python put: O(1)
retrieve: O(n + dlogd) O(n) Medium ?

642 Design Search Autocomplete System C++ Python O(p^2) O(p * t + s) Hard ?

715 Range Module C++ Python add: O(n)
remove: O(n)
query: O(logn) O(n) Hard

716 Max Stack C++ Python push: O(logn)
pop: O(logn)
popMax: O(logn)
top: O(1)
peekMax: O(1) O(n) Easy

745 Prefix and Suffix Search C++ Python ctor: O(w * l^2)
search : O(p + s) O(t) Hard

Trie