Solutions to some algorithm problems. (Mainly from leetcode)
This repository is mainly for personal use, however, it's licensed under AGPL-v3.
So use it as free as you can.
*. Time complexity is calculated using the worst case (i.e. all hash conflict)
Language Used
| Abbreviation | Language | Usage |
|---|---|---|
CPP |
C++ | Mainly for Hard and Medium Problems |
CS |
C# / CSharp | Mainly for Medium and Easy Problems |
TS |
TypeScript | Mainly for Easy Problems |
PY |
Python | Legacy |
Problem List
| ID | Problem | Solution Adopted | Perceived Difficulty | Annotated Difficulty | Time Complxity | Lang | Status |
|---|---|---|---|---|---|---|---|
| 1 | Two Sum | Hash | 1 | EASY | O(nlogn) | CPP |
L |
| 2 | Add Two Numbers | Simulation | 1 | MEDIUM | O(n) | CPP |
L |
| 3 | Longest Substring Without Repeating Characters | Sliding Window | 1 | MEDIUM | O(n) | CPP |
L |
| 4 | Median of Two Sorted Arrays | Binary Search | 7 ★ | HARD | O(logn) | CPP |
|
| 5 | Longest Palindromic Substring | Manacher | 4 | MEDIUM | O(n) | CPP |
|
| 6 | Zigzag Conversion | Simulation | 2 | MEDIUM | O(n) | CPP |
L |
| 7 | Reverse Integer | Simulation | 0 | MEDIUM | O(logn) | CPP |
L |
| 8 | String to Integer | Simulation | 0 | MEDIUM | O(n) | CS |
|
| 9 | Palindrome Number | Simulation | 0 | EASY | O(logn) | CPP |
L |
| 10 | Regular Expression Matching | Dynamic Programming | 5 | HARD | CPP |
||
| 11 | Container with Most Water | Two Pointers | 7 ★ | MEDIUM | O(n) | CS |
|
| 12 | Integer to Roman | Simulation | 0 | MEDIUM | O(logn) | CS |
|
| 13 | Roman to Integer | Simulation | 0 | EASY | O(n) | CPP |
L |
| 14 | Longest Common Prefix | Simulation | 0 | EASY | O(nm) | CPP |
L |
| 15 | 3 Sum | Hash | 5 | MEDIUM | O(n^3) | CS |
|
| 16 | 3 Sum Closest | Two Pointers | 5 | MEDIUM | O(n^2) | CS |
|
| 17 | Letter Combinations of a Phone Number | Simulation | 0 | MEDIUM | O(n*4^n) | CS |
|
| 18 | 4 Sum | Two Pointers | 5 | MEDIUM | O(n^3) | CS |
|
| 19 | Remove Nth Node From End of List | Two Pointers | 3 | MEDIUM | O(n) | CS |
|
| 20 | Valid Parentheses | Stack | 0 | EASY | O(n) | CPP |
L |
| 21 | Merge Two Sorted Lists | Simulation | 0 | EASY | O(n) | CPP |
L |
| 22 | Generate Parentheses | Simulation | 1 | MEDIUM | / | CS |
|
| 23 | Merge k Sorted Lists | Simulation | 1 | HARD | CPP |
||
| 24 | Swap Nodes in Pairs | Simulation | 2 | MEDIUM | O(n) | CS |
|
| 25 | Reverse Nodes in k-Group | Simulation | 3 | HARD | CPP |
||
| 26 | Remove Duplicates From Sorted Array | Two Pointers | 1 | EASY | O(n) | CPP |
L |
| 27 | Remove Element | Two Pointers | 2 | EASY | O(n) | CPP |
L |
| 28 | Find the Index of the First Occurrence in a String | / (Expected KMP) | 2 | EASY | O(n) | PY |
L |
| 29 | Divide | Binary Calculation | 5 | MEDIUM | O(logn) | CS |
|
| 30 | Substring with Concatenation of All Words | Sliding Window | 6 | HARD | CPP |
||
| 31 | Next Permutation | Sort | 5 | MEDIUM | O(n^2) | CS |
T |
| 32 | Longest Valid Parentheses | Dynamic Programming + Stack | 4 | HARD | CPP |
||
| 33 | Search in Rotated Sorted Array | Binary Search | 3 | MEDIUM | O(nlogn) | CS |
|
| 34 | Find First and Last Position of Element in Sorted Array | Binary Search | 2 | MEDIUM | O(nlogn) | CS |
|
| 35 | Search Insert Position | Binary Search | 1 | EASY | O(logn) | CPP |
L |
| 36 | Valid Sudoku | Simulation | 1 | MEDIUM | CS |
||
| 37 | Sudoku Solver | Simulation | 2 | HARD | / | CPP |
|
| 38 | Count And Say | Simulation | 1 | MEDIUM | O(n^2) | CPP |
L |
| 39 | Combination Sum | Dynamic Programming + Depth First Search | 4 | MEDIUM | / | CS |
|
| 40 | Combination Sum II | Dynamic Programming + Depth First Search | 4 | MEDIUM | / | CS |
|
| 41 | First Missing Positive | Simulation (Inplace) | 8 ★ | HARD | CPP |
||
| 42 | Trapping Rain Water | Simulation | 4 | HARD | CPP |
||
| 43 | Multiply String | Simulation | 2 | MEDIUM | O(n^2) | CS |
|
| 44 | Wildcard Matching | Dynamic Programming | N/A | HARD | CPP |
T | |
| 45 | Jump Game II | Dynamic Programming / Greedy Search / Simulation | 4 | MEDIUM | O(n) | CS |
|
| 46 | Permutations | Simulation | 0 | MEDIUM | O(n!) | CS |
|
| 47 | Permutations II | Simulation+Sort | 2 | MEDIUM | O(n!) | CS |
|
| 48 | Rotate Image | Simulation | 3 | MEDIUM | O(n^2) | CS |
|
| 49 | Group Anagrams | Hash | 4 | MEDIUM | O(n^2m) | CS |
|
| 50 | Pow(x,n) | Fast Power Algorithm | 3 | MEDIUM | CPP |
||
| 51 | N-Queens | Simulation | 1 | HARD | CPP |
||
| 52 | N-Queens II | Simulation | 0 | HARD | CPP |
||
| 53 | Maximum Subarray | Prefix Sum & Greedy Simulation | 2 | MEDIUM | O(n) | CPP |
LT |
| 54 | Spiral Matrix | Simulation | 2 | MEDIUM | O(n^2) | CPP |
L |
| 55 | Jump Game | Simulation | 2 | MEDIUM | O(n) | CS |
|
| 56 | Merge Intervals | Sort | 2 | MEDIUM | O(nlogn) | CS |
|
| 57 | Insert Intervals | Simulation + Binary Search (optional) | 4 | MEDIUM | O(n) | CS |
|
| 58 | Length of Last Word | Simulation | 0 | EASY | O(n) | CPP |
L |
| 59 | Spiral Matrix II | Simulation | 2 | MEDIUM | O(n^2) | CPP |
L |
| 60 | Permutation Sequence | Combinatorics | 5 | HARD | CPP |
||
| 61 | Rotate List | Simulation | 2 | MEDIUM | O(n) | CPP |
L |
| 62 | Unique Paths | Dynamic Programming | 0 | MEDIUM | O(nm) | CS |
|
| 63 | Unique Paths II | Dynamic Programming | 0 | MEDIUM | O(nm) | CS |
|
| 64 | Minimum Path Sum | Dynamic Programming | 0 | MEDIUM | O(nm) | CS |
|
| 65 | Valid Number | Simulation | 2 | HARD | CPP |
||
| 66 | Plus One | Simulation | 1 | EASY | O(n) | CPP |
L |
| 67 | Add Binary | Simulation | 1 | EASY | O(n) | CPP |
L |
| 68 | Text Justification | Simulation | 2 | HARD | CPP |
||
| 69 | Sqrt(X) | Binary Search | 1 | EASY | O(logn) | CPP |
LT |
| 70 | Climbing Stairs | Dynamic Programming | 0 | EASY | CPP |
||
| 71 | Simplify Path | Stack | 1 | MEDIUM | O(n) | CS |
|
| 72 | Edit Distance | Dynamic Programming | 6 | MEDIUM | O(n^3) | CS |
T |
| 73 | Set Matrix Zeros | Simulation + Intuition | 2 | MEDIUM | O(mn) | CPP |
L |
| 74 | Search A 2D Matrix | Simulation | 2 | MEDIUM | O(m+n) | CPP |
LT |
| 75 | Sort Colors | Two Pointers | 4 | MEDIUM | O(n) | CS |
|
| 76 | Minimum Window Substring | Sliding Window | 6 | HARD | CPP |
||
| 77 | Combinations | Simulation | 2 | MEDIUM | / | CS |
|
| 78 | Subsets | Simulation | 1 | MEDIUM | O(2^n) | CS |
|
| 79 | Word Search | Simulation | 1 | MEDIUM | O(n^2*m^2) | CS |
T |
| 80 | Remove Duplicates From Sorted Array II | Simulation (Two Pointers) | 3 | MEDIUM | CS |
L | |
| 81 | Search In Rotated Sorted Array II | Simulataion | N/A | MEDIUM | CS |
LT | |
| 82 | Remove Duplicates From Sorted Array II | Simulation (Two Pointers) | 2 | MEDIUM | CPP |
L | |
| 83 | Remove Duplicates From Sorted Array | Simulation (Two Pointers) | 1 | EASY | CPP |
L | |
| 84 | Largest Rectangle in Histogram | Stack | 6 | HARD | CPP |
||
| 85 | Maximal Rectangle | Prefix Sum | 5 | HARD | CPP |
||
| 86 | Partition List | Simulation | 1 | MEDIUM | O(n) | CS |
|
| 87 | Scramble String | Dynamic Programming + Intuition | 7 ★ | HARD | O(n^4) | CPP |
|
| 88 | Merge Sorted Array | Simulation (Two Pointers) | 1 | EASY | O(n) | CS |
|
| 89 | Gray Code | Intuition + Simulation | 4 | MEDIUM | O(2^n) | CS |
|
| 90 | Subsets II | Simulation | 2 | MEDIUM | CPP |
L | |
| 91 | Decode Ways | Dynamic Programming | 1 | MEDIUM | O(n) | CS |
|
| 92 | Reverse Linked List | Simulation | 2 | MEDIUM | O(n) | CPP |
L |
| 93 | Restore IP Address | Simulation | 1 | MEDIUM | / | CS |
|
| 94 | Binary Tree Mid Order Traversal | Simulation | 1 | EASY | CPP |
L | |
| 95 | Unique Binary Search Trees II | Simulation | 4 | MEDIUM | / | CPP |
|
| 96 | Unique Binary Search Trees | Dynamic Programming | 2 | MEDIUM | O(n^2) | CS |
|
| 97 | Interleaving String | Dynamic Programming | 6 | MEDIUM | / | / | |
| 97F | Interleaving String (Follow-up) | Dynamic Programming (Scrolling Array) | 6 | MEDIUM | O(n^2) | CPP |
|
| 98 | Validate Binary Search Tree | Simulation | 1 | MEDIUM | O(n) | CS |
|
| 99 | Recover Binary Search Tree | Inorder Traversal | 5 | MEDIUM | O(n) | CPP |
|
| 99F | Recover Binary Search Tree (Follow-up) | Inorder Traversal + Simulation | 5 | MEDIUM | O(n) | CPP |
|
| 100 | Same Tree | Simulation | 0 | EASY | O(n) | CPP |
L |
| 101 | Symmetric Tree | Simulation | 1 | EASY | O(n) | CPP |
|
| 102 | Binary Tree Level Order Traversal | Simulation | 0 | MEDIUM | O(n) | CPP |
L |
| 103 | Binary Tree Zig-zag Level Order Traversal | Simulation | 1 | MEDIUM | O(n) | CPP |
|
| 104 | Maximum Depth of Binary Tree | Depth-first Search | 0 | EASY | O(n) | CS |
|
| 105 | Construct Binary Tree from Preorder and Inorder Traversal | Simulation | 1 | MEDIUM | O(n) | CPP |
|
| 106 | Construct Binary Tree from Inorder and Postorder Traversal | Simulation | 1 | MEDIUM | O(n) | CPP |
|
| 107 | Binary Tree Level Order Traversal II | Simulation | 0 | MEDIUM | O(n) | CPP |
|
| 108 | Convert Sorted Array to Binary Search Tree | Divide & Conquer | 1 | MEDIUM | O(n) | CPP |
|
| 109 | Convert Sorted List to Binary Search Tree | Inorder Traversal | 4 | MEDIUM | O(n) | CPP |
|
| 110 | Balanced Binary Tree | Simulation | 0 | EASY | O(n) | CPP |
|
| 111 | Minimum Depth of Binary Tree | Simulation | 0 | EASY | O(n) | CPP |
|
| 112 | Path Sum | Simulation | 0 | EASY | O(n) | CPP |
|
| 113 | Path Sum II | Simulation | 0 | MEDIUM | / | CPP |
|
| 114 | Flatten Binary Tree To Linked List | Simulation | N/A | MEDIUM | O(n) | CS |
T |
| 115 | Distinct Subsequences | Dynamic Programming | 5 | HARD | / | CPP |
L |
| 116 | Populating Next Right Pointers in Each Node | BFS | 1 | MEDIUM | / | CPP |
P |
| 117 | Populating Next Right Pointers in Each Node II | Depth-first Search | 1 | MEDIUM | / | CPP |
|
| 117F | Populating Next Right Pointers in Each Node II (Follow-up) | Depth-first Search | 4 | MEDIUM | / | CPP |
|
| 118 | Pascal's Triangle | Dynamic Programming | 0 | EASY | O(n^2) | CPP |
|
| 119 | Pascal's Triangle II | Dynamic Programming | 0 | EASY | O(n^2) | CPP |
|
| 119F | Pascal's Triangle II (Follow-up) | Dynamic Programming (Scrolling Array) | 1 | EASY | O(n^2) | CPP |
|
| 120 | Triangle | Dynamic Programming | 1 | MEDIUM | O(n^2) | CS |
|
| 121 | Best Time to Buy and Sell Stock | Dynamic Programming | 0 | EASY | O(n) | CPP |
L |
| 122 | Best Time to Buy and Sell Stock II | Dynamic Programming | 1 | MEDIUM | O(n) | CS |
|
| 123 | Best Time to Buy and Sell Stock III | Dynamic Programming | 5 | HARD | CPP |
||
| 124 | Binary Tree Maximum Path Sum | Dynamic Programming | 3 | HARD | CPP |
||
| 125 | Valid Palindrome | Simulation | 0 | EASY | O(n) | CS |
|
| 126 | Word Ladder II | Breadth-first Search + Depth-first Search | 6 | HARD | / | CPP |
|
| 127 | Word Ladder | Breadth-first Search | 6 | HARD | O(n^2*m^2) | CPP |
|
| 128 | Longest Consecutive Sequence | Hashing + Union Find Algorithm | 4 | MEDIUM | O(n^2) | CPP |
|
| 129 | Sum Root to Leaf Numbers | DFS | 0 | MEDIUM | O(n) | CPP |
|
| 130 | Surrounded Regions | Simulation | 1 | MEDIUM | O(nm) | CPP |
|
| 131 | Palindrome Partitioning | Simulation | 2 | MEDIUM | / | PY |
L |
| 132 | Palindrome Partitioning II | Simulation | 5 | HARD | / | CPP |
L |
| 133 | Clone Graph | DFS | 1 | MEDIUM | O(V^2E) | CPP |
|
| 134 | Gas Station | Greedy Strategy | 3 | MEDIUM | O(n) | CPP |
|
| 135 | Candy | Greedy Strategy + Sort | 4 | HARD | CPP |
||
| 136 | Single Number | Binary Calculation | 2 | EASY | O(n) | CPP |
L |
| 137 | Single Number II | Ternary Calculation | 3 | MEDIUM | O(nlogn) | CPP |
|
| 138 | Copy List with Random Pointers | Simulation | 1 | MEDIUM | O(n) | CPP |
|
| 139 | Word Break | Dynamic Programming + String Hash | 3 | MEDIUM | O(n^3) | CPP |
|
| 140 | Word Break II | Dynamic Programming + Depth-First Search + String Hash | 5 | HARD | CPP |
||
| 141 | Linked List Cycle | Simulation | 1 | EASY | / | / | |
| 141F | Linked List Cycle (Follow-up) | Two Pointers | 4 | EASY | O(n) | CPP |
|
| 142 | Linked List Cycle II | Simulation | 1 | MEDIUM | / | / | |
| 142F | Linked List Cycle II (Follow-up) | Two Pointers + Math | 6 | MEDIUM | O(n) | CPP |
|
| 143 | Reorder Linked List | Simulation | 1 | MEDIUM | O(n) | CPP |
S |
| 144 | Binary Tree Preorder Traversal | Simulation | 0 | EASY | O(n) | CPP |
L |
| 145 | Binary Tree Postorder Traversal | Simulation | 0 | EASY | O(n) | CPP |
L |
| 146 | LRU Cache | Hash + Double-Ended Queue | 3 | MEDIUM | O(n) | CPP |
|
| 147 | Insertion Sort List | Simulation | 1 | MEDIUM | O(n^2) | CPP |
|
| 148 | Sort List | Merge Sort | 3 | MEDIUM | O(nlogn) | CPP |
|
| 149 | Max Points on a Line | Simulation | 1 | HARD | O(n^3) | CS |
L |
| 150 | Evaluate Reverse Polish Notation | Stack | 1 | MEDIUM | O(n) | CPP |
L |
| 160 | Intersection of Two Linked Lists | Simulation | 1 | EASY | / | / | |
| 160F | Intersection of Two Linked Lists (Follow-up) | Simulation | 1 | EASY | O(n) | CPP |
|
| 172 | Factorial Trailing Zeroes | Simulation | 0 | MEDIUM | O(logn) | CS |
|
| 174 | Dungeon Game | Dynamic Programming | 7 ★ | HARD | CPP |
||
| 184 | Best Time to Buy and Sell Stock IV | Dynamic Programming | 5 | HARD | CPP |
||
| 189 | Rotate Array | Simulation | 1 | MEDIUM | / | / | |
| 189F | Rotate Array (Follow-up) | Simulation + Math | 3 | MEDIUM | O(n) | CPP |
|
| 199 | Binary Tree Right Side View | Simulation | 1 | MEDIUM | O(n) | CPP |
|
| 200 | Number of Islands | Breadth-first Search | 0 | MEDIUM | O(nm) | CS |
|
| 206 | Reversed Linked List | Simulation | 0 | EASY | O(n) | CPP |
|
| 207 | Course Schedule | Topological Sort | 0 | MEDIUM | O(n) | CS |
|
| 214 | Shortest Palindrome | Rabin-Karp | 4 | HARD | CPP |
||
| 218 | The Skyline Problem | Heap + Sort | 5 | HARD | CPP |
||
| 225 | Implement Stack Using Queues | Simulation | 0 | EASY | O(nm) | / | |
| 225F | Implement Stack Using Queues (Follow-up) | Simulation | 0 | EASY | O(nm) | CS |
|
| 226 | Invert Binary Tree | Simulation | 0 | EASY | O(n) | CPP |
|
| 230 | K-th Smallest Element in a BST | Inorder Traversal | 1 | MEDIUM | O(n) | CPP |
|
| 231 | Power of Two | Simulation | 0 | EASY | O(logn) | CS |
|
| 232 | Implement Queue using Stacks | Simulation | 0 | EASY | O(nm) | / | |
| 232F | Implement Queue using Stacks (Follow-up) | Simulation | 0 | EASY | O(n) | CS |
|
| 233 | Number of Digit One | Combinatorics + Dynamic Programming | 6 | HARD | CPP |
||
| 234 | Palindrome Linked List | Simulation | 0 | EASY | / | / | |
| 234F | Palindrome Linked List (Follow-up) | Simulation | 1 | EASY | O(n) | CPP |
|
| 236 | Lowest Common Ancestor of a Binary Tree | Simulation | 1 | MEDIUM | O(n) | CPP |
|
| 238 | Product of Array Except Self | Prefix Sum | 0 | MEDIUM | / | / | |
| 238F | Product of Array Except Self (Follow-up) | Prefix Sum | 1 | MEDIUM | O(n) | CPP |
|
| 273 | Integer To English Words | Simulation | 1 | HARD | O(n) | CPP |
|
| 282 | Expression Add Operators | Simulation | 2 | HARD | / | CPP |
|
| 283 | Move Zeroes | Two Pointers | 1 | EASY | O(n) | CS |
|
| 292 | Nim Game | Gaming Theory + Dynamic Programming | 3 | EASY | CPP |
||
| 295 | Find Median from Data Stream | Heap | 5 | HARD | CPP |
||
| 299 | Bulls and Cows | Simulation | 1 | MEDIUM | O(n) | CS |
|
| 297 | Serialize and Deserialize Binary Tree | Breadth-first Search | 2 | HARD | O(n) | CPP |
|
| 301 | Remove Invalid Parentheses | Depth-first Search | 6 | HARD | / | CPP |
|
| 303 | Range Sum Query Immutable | Prefix Sum | -1 | EASY | O(n) | CS |
|
| 310 | Minimum Height Tree | Dynamic Programming | 3 | MEDIUM | O(n) | CS |
|
| 312 | Burst Balloons | Dynamic Programming | 6 | HARD | CPP |
||
| 315 | Count of Smaller Numbers After Self | Binary Index Tree | 3 | HARD | CPP |
||
| 322 | Coin Change | Dynamic Programming | 1 | MEDIUM | O(nm) | CS |
|
| 327 | Count of Range Sum | Binary Index Tree + Hash + Binary Search Tree + Prefix Sum | 6 | HARD | CPP |
||
| 329 | Longest Increasing Path | Topological Sort | 4 | HARD | O(mn) | CPP |
|
| 330 | Patching Array | Greedy Strategy | 4 | HARD | CS |
T | |
| 375 | Verify Pre-order Serialization of a Binary Tree | Depth-first Search (DFS) | 1 | MEDIUM | O(n) | CS |
|
| 332 | Reconstruct Itinerary | Eulerian Circuit (Hierholzer Algorithm) + Greedy Strategy(Sort) + Hash | 8 ★ | HARD | O(n^2) | CPP |
|
| 367 | Valid Perfect Square | Binary Search | 0 | EASY | O(logn) | CPP |
|
| 375 | Guess Number Higher or Lower II | Dynamic Programming (Range) | 3 | MEDIUM | O(n^3) | CPP |
|
| 391 | Perfect Rectangle | Simulation + Intuition | 5 | HARD | O(nlogn) | CPP |
|
| 396 | Rotate Function | Simulation | 1 | MEDIUM | O(n) | CPP |
|
| 403 | Frog Jump | Breadth-first Search | 3 | HARD | CPP |
||
| 407 | Trapping Water II | Heap | 5 | HARD | O(nm*log(nm)) | CPP |
|
| 410 | Split Array Largest Sum | Dynamic Programming | N/A | HARD | CPP |
T | |
| 416 | Partition Equal Subset Sum | Dynamic Programming (Backpack Problem) | 1 | MEDIUM | O(n^3) | CS |
|
| 437 | Path Sum III | Prefix Sum + Hash | 3 | MEDIUM | O(n^2) | CPP |
|
| 438 | Find All Anagrams In a String | Sliding Window | 2 | MEDIUM | O(n) | CS |
|
| 440 | K-th Smallest in Lexicographical Order | Simulation | 5 | HARD | O(logn) | CPP |
|
| 446 | Arithmetic Slices II - Subsequence | Dynamic Programming + Hash | 5 | HARD | O(n^3) | CPP |
|
| 458 | Poor Pig | Math | 9 ★ | HARD | Depend on std implementation |
CPP |
|
| 467 | Unique Substrings in Wraparound String | Dynamic Programming | 1 | MEDIUM | O(n) | CS |
|
| 472 | Concatenated Words | Trie + Depth-first Search | 6 | HARD | / | CPP |
|
| 474 | Ones And Zeros | Dynamic Programming (Backpack) | 2 | MEDIUM | O(mnp+pq) | CS |
ST |
| 480 | Sliding Window Median | Heap + Redundancy | 6 | HARD | O(nlogn)? | CPP |
|
| 493 | Reverse Pairs | Merge Sort | 5 | HARD | O(nlogn) | CPP |
|
| 494 | Target Sum | Dynamic Programming (Backpack) | 1 | MEDIUM | O(ns) | CS |
S |
| 502 | IPO | Greedy Strategy | 2 | HARD | O(nlogn) | CPP |
|
| 514 | Freedom Trail | Dynamic Programming | 3 | HARD | O(mn^2) | CPP |
|
| 518 | Coin Change II | Dynamic Programming | 1 | MEDIUM | O(nm) | CS |
|
| 543 | Diameter of Binary Tree | Simulation | 0 | EASY | O(n) | CPP |
|
| 547 | Number of Provinces | Breadth-first Search | 2 | MEDIUM | O(n^2) | CPP |
|
| 552 | Student Attendance Record II | Dynamic Programming | 2 | HARD | O(n) | CPP |
|
| 560 | Subarray Sum Equals K | Hashing + Prefix Sum | 2 | MEDIUM | O(n^2) | CS |
|
| 598 | Range Addition II | Simulation | 0 | EASY | CPP |
||
| 600 | Non-negative Integers without Consecutive Ones | Dynamic Programming | 3 | HARD | O(logn) | CPP |
|
| 629 | K Inverse Pairs Array | Dynamic Programming | 5 | HARD | O(nk) | CPP |
|
| 632 | Smallest Range Covering Elements From K Lists | Greedy Strategy (Heap) | 3 | HARD | O(nlogn) | CPP |
|
| 639 | Decode Ways II | Dynamic Programming | 2 | HARD | O(n) | CPP |
|
| 664 | Strange Printer | Dynamic Programming | 8 ★ | HARD | O(n^3) | CPP |
|
| 679 | 24 Game | Simulation | 2 | HARD | CPP |
||
| 685 | Redundant Connection II | Union-Find Algorithm | 3 | HARD | O(nlogn) | CPP |
|
| 699 | Falling Squares | Segment Tree + Discretization | 5 | HARD | O(nlogn) | CPP |
|
| 739 | Daily Temperature | Stack | 0 | MEDIUM | O(n) | CPP |
|
| 753 | Cracking the Safe | Eulerian Circuit (Hierholzer Algorithm) | 9 ★ | HARD | O(k^2n) | CPP |
|
| 765 | Couples Holding Hands | Union-find Algorithm | 5 | HARD | O(n^2) | CPP |
|
| 768 | Max Chunks to Make Sorted II | Greedy Strategy (Monotonic Stack) | 3 | HARD | O(n) | CPP |
|
| 773 | Sliding Puzzle | Breadth-first Search | 3 | HARD | / | CPP |
|
| 778 | Swim in Rising Water | Greedy Strategy(Heap) + Breadth-first Search | 3 | HARD | O(n^2logn) | CPP |
|
| 793 | Preimage Size of Factorial Zeroes Function | Primary Math + Binary Search | 6 | HARD | CPP |
||
| 801 | Minimum Swaps To Make Sequences Increasing | Dynamic Programming | 1 | HARD | O(n) | CPP |
|
| 805 | Split Array With Same Average | Divide And Conquer + Hash + Depth-first Search | 5 | HARD | O(n*2^n) | CPP |
|
| 827 | Making a Large Island | Breadth-first Search | 2 | HARD | O(n^2) | CPP |
|
| 828 | Counting Unique Characters of All Substrings | Simulation (Counting) | 4 | HARD | O(n) | CPP |
|
| 829 | Consecutive Numbers Sum | Primary Math | 2 | HARD | CPP |
||
| 834 | Sum of Distances In Tree | Dynamic Programming + Depth-first Search | 4 | HARD | O(n) | CPP |
|
| 847 | Shortest Path Visiting All Nodes | Breadth-first Search + Bit Mask | 6 | HARD | O(n^2*2^n) | CPP |
|
| 850 | Rectangle Area II (Acceptable Solution) | Simulation | 3 | HARD | O(n^3) | / | |
| 850F | Rectangle Area II (Optimal Solution) | Computational Geometry (Sweeping Line) + Segment Tree + Discretization (Hashing) | 7 ★ | HARD | O(nlogn) | CPP |
|
| 862 | Shortest Subarray with Sum at Least K | Dynamic Programming (Monotonic Queue + Binary Search) + Prefix Sum | 5 | HARD | O(nlogn) | CPP |
|
| 864 | Shortest Path to Get All Keys | Bit Mask + Breadth-first Search | 4 | HARD | O(nm2^k) | CPP |
|
| 871 | Minimum Number of Refueling Stops | Greedy Strategy (Heap) | 2 | HARD | O(nlogn) | CPP |
|
| 878 | Nth Magical Number | Math Theory + Binary Search | 7 ★ | HARD | CPP |
||
| 887 | Super Egg Drop | Induction + Dynamic Programming + Binary Search | 8 ★ | HARD | / | CPP |
|
| 891 | Sum of Subsequence Width | Primary Math + Sort | 2 | HARD | O(nlogn) | CPP |
|
| 895 | Max Frequency Stack | Heap | 1 | HARD | O(nlogn) | CPP |
|
| 902 | Numbers At Most N Given Digit Set | Simulation | 2 | HARD | O(logn) | CPP |
|
| 956 | Tallest Billboard | Dynamic Programming + Hash | N/A | HARD | O(ns^2) | CPP |
T |
| 968 | Binary Tree Cameras | Dynamic Programming | 4 | HARD | O(n) | CPP |
|
| 975 | Odd Even Jump | Dynamic Programming + Binary Search Tree | 4 | HARD | O(nlogn) | CPP |
|
| 996 | Number of Squareful Arrays | Bit Mask + Dynamic Programming | N/A | HARD | O(sqrt(d) n^2*2^n) | CPP |
T |
| 1012 | Numbers With Repeated Digits | Dynamic Programming | 5 | HARD | / | CPP |
|
| 1025 | Divisor Game | Induction / Gaming Theory | 3 | EASY | CPP |
||
| 1095 | Find in Mountain Array | Binary Search | 4 | HARD | O(logn) | CPP |
|
| 1106 | Parsing a Boolean Expression | Stack | 2 | HARD | O(n) | CPP |
|
| 1137 | N-th Tribonacci Number | Dynamic Programming | 0 | EASY | O(n) | CPP |
|
| 1210 | Minimum Moves to Reach Target with Rotations | Breadth-first Search | 2 | HARD | O(n^2) | CPP |
|
| 1220 | Count Vowels Permutation | Dynamic Programming | 0 | HARD | O(n) | CPP |
|
| 1223 | Dice Roll Simulation | Dynamic Programming | 2 | HARD | O(nm) | CPP |
|
| 1235 | Maximum Profit In Job Scheduling | Dynamic Programming + Discretization + Sort | 2 | HARD | O(nlogn) | CPP |
|
| 1250 | Check If It's a Good Array | Primary Math | 1 | HARD | O(nlogn) | CPP |
|
| 1261 | Find Elements in a Contaminated Binary Tree | Breadth-first Search | 0 | MEDIUM | O(n) | CS / TS |
|
| 1263 | Minimum Moves to Move a Box to Their Target Location | Breadth-first Search | 4 | HARD | O(n^4) | CPP |
|
| 1269 | Number of Ways to Stay in the Same Place After Some Steps | Dynamic Programming | 2 | HARD | O(n^2) | CPP |
|
| 1289 | Minimum Falling Path Sum II | Dynamic Programming | 1 | HARD | O(n^2) | CPP |
|
| 1298 | Maximum Candies You Can Get from Boxes | Topological Sort | 3 | HARD | O(n) | CPP |
|
| 1320 | Minimum Distance to Type a Word Using Two Fingers | Dynamic Programming | 1 | HARD | O(nk^2) | CPP |
|
| 1326 | Minimum Number of Taps to Open to Water a Garden | Greedy Strategy (Sort) | 4 | HARD | O(nlogn) | CPP |
|
| 1335 | Minimum Difficulty of a Job Schedule | Dynamic Programming | 1 | HARD | O(dn^2) | CPP |
|
| 1345 | Jump Game IV | Breadth-first Search | 3 | HARD | CPP |
||
| 1349 | Maximum Students Taking Exam | Bit Mask + Dynamic Programming | 3 | HARD | O(nm2^(2m)) | CPP |
|
| 1359 | Count All Valid Pickup and Delivery Options | Combinatorics | 0 | HARD | O(n) | CPP |
|
| 1377 | Frog Position After T Seconds | Depth-first Search | 1 | HARD | O(n) | CPP |
|
| 1392 | Longest Happy Prefix | Suffix Array (KMP) | 1 | HARD | O(n) | CPP |
|
| 1402 | Reducing Dishes | Dynamic Programming | 3 | HARD | O(n^2) | CPP |
|
| 1411 | Number of Ways to Paint Nx3 Grid | Dynamic Programming | 3 | HARD | O(n) | CPP |
|
| 1416 | Restore the Array | Dynamic Programming | 2 | HARD | O(nlogk) | CPP |
|
| 1420 | Build Array Where You Can Find The Maximum Exactly K Comparisons | Dynamic Programming + Prefix Sum + Scrolling Array | 5 | HARD | O(n^2m^2) | CPP |
|
| 1425 | Constrained Subsequence Sum | Dynamic Programming + Sliding Window | 3 | HARD | O(n) | CPP |
|
| 1434 | Number of Ways to Wear Different Hats to Each Other | Bit Mask + Dynamic Programming | 4 | HARD | O(nm*2^n) | CPP |
|
| 1444 | Number of Ways of Cutting a Pizza | Dynamic Programming + Prefix Sum | 4 | HARD | O(nmk(m+n)) | CPP |
|
| 1463 | Cherry Pickup II | Dynamic Programming | 5 | HARD | O(nm^2) | CPP |
|
| 1473 | Paint House III | Dynamic Programming | 4 | HARD | O(n^2m^2) | CPP |
|
| 1499 | Max Value of Equation | Greedy Strategy (Sliding Window) | 2 | HARD | O(n) | CPP |
|
| 1515 | Best Position for a Service Center | Simulated Annealing | 6 | HARD | CS |
L | |
| 1537 | Get the Maximum Score | Two Pointers | 3 | HARD | O(n+m) | CPP |
|
| 1547 | Minimum Cost to Cut a Stick | Dynamic Programming | 3 | HARD | O(m^3) | CPP |
|
| 1610 | Maximum Number of Visible Points | Computational Geometry + Sort | 4 | HARD | CPP |
||
| 1665 | Minimum Initial Energy to Finish Tasks | Greedy Strategy (Sort) + Simulation | 4 | HARD | O(nlogn) | CPP |
|
| 1671 | Minimum Number of Removals to Make Mountain Array | Dynamic Programming (LIS) + Binary Search | 3 | HARD | O(nlogn) | CPP |
|
| 1681 | Minimum Incompatibility | Dynamic Programming + Bit Mask + Hash | 4 | HARD | O(n2^n) | CPP |
|
| 1723 | Find Minimum Time to Finish All Jobs | Bit Mask + Dynamic Programming | 4 | HARD | O(k*3^n) | CPP |
|
| 1739 | Building Boxes | Binary Search | 6 | HARD | O(logn) | CPP |
|
| 1751 | Maximum Number of Events That Can Be Attended II | Dynamic Programming + Discretization (Hash + Sort) | 3 | HARD | O(nlogn+nk) | CPP |
|
| 1770 | Maximum Score from Performing Multiplication Operations | Dynamic Programming | 1 | HARD | O(m^2) | CPP |
|
| 1793 | Maximum Score of a Good Subarray | Two Pointers | 2 | HARD | O(n) | CPP |
|
| 1840 | Maximum Building Height | Stack + Sort + Math (Geometry) | 4 | HARD | O(nlogn) | CPP |
|
| 1851 | Minimum Interval to Include Each Query | Greedy Strategy (Heap+Sort) + Two Pointers | 4 | HARD | O(nlogn) | CPP |
|
| 1866 | Number of Ways to Rearrange Sticks With K Sticks Visible | Dynamic Programming + Combinatorics | 7 | HARD | O(nk) | CPP |
|
| 1884 | Egg Drop With 2 Eggs and N Floors | Dynamic Programming + Induction + Binary Search | 6 | MEDIUM | O(logn) | CPP |
|
| 1931 | Painting a Grid With Three Different Colors | Dynamic Programming | 2 | HARD | O(n*3^(2m)) | CPP |
|
| 1944 | Number of Visible People in a Queue | Monotonic Stack | 4 | HARD | CPP |
||
| 1969 | Minimum Non-Zero Product of the Array Elements | Fast Power Algorithm | 4 | MEDIUM | O(nlogn) | CS |
|
| 1976 | Number of Ways to Arrive at Destination | Dijkstra (Heap) + Topological Sort | 5 | MEDIUM | O(n^2logn) | CPP |
|
| 1994 | The Number of Good Subsets | Bit Mask + Dynamic Programming | 5 | HARD | O(m*2^m+logn) | CPP |
|
| 2097 | Valid Arrangement of Pairs | Eulerian Circuit (Hierholzer Algorithm) + Constant Reduction (TLE Avoidance) + Hash | 8 ★ | HARD | O(n^2) | CPP |
|
| 2147 | Number of Ways to Divide a Long Corridor | Simulation | 1 | HARD | O(n) | CPP |
|
| 2156 | Find Substring With Given Hash Value | Primary Math + Sliding Window (Rolling Hash) | 3 | HARD | O(n) | CPP |
|
| 2129 | Capitalize the Title | Simulation | 1 | EASY | O(n) | CS |
|
| 2218 | Maximum Value of K Coins From Piles | Dynamic Programming + Prefix Sum | 3 | HARD | O(nk)? | CPP |
|
| 2251 | Number of Flowers in Full Bloom | Two Pointers + Sort | 2 | HARD | O(nlogn) | CPP |
|
| 2258 | Escape the Spreading Fire | Breadth-first Search + Binary Search | 6 | HARD | O(nmlog(nm)) | CPP |
|
| 2262 | Total Appeal of a String | Simulation (Counting) | 4 | HARD | O(n) | CPP |
|
| 2312 | Selling Pieces of Wood | Dynamic Programming | 4 | HARD | O(mn(m+n)) | CPP |
|
| 2318 | Number of Distinct Roll Sequences | Dynamic Programming | 2 | HARD | O(n) | CPP |
|
| 2368 | Reachable Nodes With Restrictions | Breadth-first Search | 0 | MEDIUM | O(n) | CS |
|
| 2369 | Check if There is a Valid Partition For The Array | Dynamic Programming | 0 | MEDIUM | O(n) | CPP |
|
| 2386 | Find the K-Sum of an Array | Sort + Heap | 7 | HARD | O(nlogn+klogk) | CPP |
|
| 2407 | Longest Increasing Subsequence | Segment Tree + Dynamic Programming | 2 | HARD | O(nlogn) | CPP |
|
| 2426 | Number of Pairs Satisfying Inequality | Binary Indexed Tree | 2 | HARD | O(nlogn) | CPP |
|
| 2454 | Next Greater Element IV | Monotonic Stack | 5 | HARD | O(n) | CPP |
|
| 2509 | Cycle Length Queries in a Tree | Binary Operation | 4 | HARD | O(n) | CPP |
|
| 2549 | Count Distinct Numbers on Board | Simulation | -1 | EASY | O(1) | TS |
|
| 2569 | Handling Sum Queries After Update | Segment Tree | 5 | HARD | O(nlogn) | CPP |
|
| 2575 | Find the Divisibility Array of a String | Simulation | 0 | MEDIUM | O(n) | TS |
|
| 2580 | Count Ways to Group Overlapping Ranges | Simulation | 0 | MEDIUM | O(nlogn) | CPP |
|
| 2617 | Minimum Number of Visited Cells in a Grid | Heap + Breadth-first Search | 6 | HARD | O(nlogn) | CPP |
|
| 2642 | Design Graph With Shortest Path Calculator | Shortest Path | 2 | HARD | O(n^3logn) | CPP |
|
| 2671 | Frequency Tracker | Hash | 1 | MEDIUM | O(nm) | TS |
|
| 2681 | Power of Heroes | Sort | 3 | HARD | O(nlogn) | CPP |
|
| 2684 | Maximum Number of Moves in a Grid | Dynamic Programming | 0 | MEDIUM | O(mn) | CS |
|
| 2736 | Maximum Sum Queries | Sort + Discretization + Segment Tree + Binary Search (BST) | 6 | HARD | O(nlogn) | CPP |
|
| 2789 | Find the Minimum Possible Sum of a Beautiful Array | Greedy Strategy (Simulation) | 1 | MEDIUM | O(n) | CS |
|
| 2834 | Find the Minimum Possible Sum of a Beautiful Array | Greedy Strategy (Math) | 1 | MEDIUM | O(1) | CS |
|
| 2864 | Maximum Odd Binary Number | Greedy Strategy (Simulation) | -1 | EASY | O(n) | TS |
|
| 2908 | Minimum Sum of Mountain Triplets I | Simulation | -2 | EASY | O(n^2) | TS |
|
| 2909 | Minimum Sum of Mountain Triplets II | Monotonic Stack | 3 | MEDIUM | O(n) | CS |
|
| 2926 | Maximum Balanced Subsequence | Segment Tree + Dynamic Programming + Discretization | 3 | HARD | O(nlogn) | CPP |
|
| 2940 | Find Building Where Alice and Bob Can Meet | Binary Search + Monotonic Stack + Sort | 5 | HARD | O(nlogn) | CPP |
|
| 2952 | Minimum Number of Coins to be Added | Sort + Greedy Strategy | 4 | MEDIUM | O(nlogn) | CS |
|
| 3027 | Find the Number of Ways to Place People II | Simulation + Sort | 1 | HARD | O(n) | CPP |
|
| LCR126 | Fibonacci Number | Dynamic Programming | 0 | EASY | O(n) | CPP |
|
| LCR187 | Ice Breaking Game | Dynamic Programming (Joseph Ring) | 3 | EASY | O(n) | CPP |
Simulation means the problem can be solved using Brute Force algorithm (Do what you are asked to do)
| ID | Problem | Annotated Difficulty | Status |
|---|---|---|---|
| Nothing Now |
| ID | Problem | Solution Adopted | Time/Space Complexity | Optimal Solution | Time/Space Complexity |
|---|---|---|---|---|---|
| 15 | 3 Sum | Hash | O(n^3)* | Two Pointers | O(n^2) |
| 31 | Next Permutation | Selection Sort | O(n^2) | Sort (Reverse) | O(n) |
| 43 | Multiply String | Simulation | O(n^2) | Fast Fourier Transform | O(nlogn) |
| 70 | Climbing Stairs | Dynamic Programming | O(n) | Dynamic Programming + Matrix Fast Power Algorithm | O(logn) |
| 74 | Search A 2D Matrix | Simulation | O(n+m) | Binary Search | O(logn+logm) |
| 81 | Search In Rotated Sorted Array II | Simulation | O(n) | Binary Search | O(logn) |
| 143 | Reorder List | Simulation | S(n) | Linked List Reverse | S(1) |
| 214 | Shortest Palindrome | Rabin-Karp | O(n^2)* | Manacher | O(n) |
| LCR126 | Fibonacci Number | Dynamic Programming | O(n) | Dynamic Programming + Matrix Fast Power Algorithm | O(logn) |
*. Worst case of hash function
T: An accepted but time-consuming algorithmS: An accepted but space-consuming algorithmL: This is a legacy (old) submissionP: Follow-up challenge incomplete
It's RIDICULOUS to see the mismatched difficulty annotated in the problem set (e.g. HARD NQueens)
Perceived difficulty is a subjective rating to a problem. The criteria might be subject to the personal experience.
| Rank | -2 | -1 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Difficulty | TU- | TU | TU+ | EZ- | EZ | EZ+ | MD- | MD | MD+ | HD- | HD | HD+ | IN- | IN | IN+ |
-
TU: Tutorial -
EZ: Easy -
MD: Medium -
HD: Hard -
IN: Inferno