[LintCode]——目錄

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Yet Another Source Code for LintCode

Current Status : 232AC / 289ALL in Language C++, Up to date (2016-02-10)
For more problems and solutions, you can see my LintCode repository.
I'll keep updating for full summary and better solutions. See cnblogs to get details or click problem's Note directly. Tip means has been added tips and sketch (* means has note at cnblogs).
This context template fork from kamyu104 , thanks them very much!

Algorithms

• Array
• Backtracking
• Binary Search
• Binary Search Trees
• Bit Manipulation
• Breadth-First Search
• Data Structure
• Depth-First Search
• Dynamic Programming
• Greedy
• Hash Tables
• Heap
• Linked List
• Math
• OO Design
• Queue
• Recursion
• Sort
• Stack
• String
• System Design
• Tree

Array PID# Title Source Time Space Difficulty Tag Note 6 Merge Sorted Array C++ O(m+n) O(1) Easy LeetCode Tip 8 Rotate String C++ O(n) O(1) Easy LeetCode Tip 9 Fizz Buzz C++ O(n) O(1) Easy Tip 30 Insert Interval C++ O(n) O(1) Easy LeetCode, EPI Tip 31 Partition Array C++ O(n) O(1) Medium Tip Two Pointers 32 Minimum Window Substring C++ O(n) O(1) Medium LeetCode todo 38 Search a 2D Matrix II C++ O(m+n) O(1) Medium EPI Tip 39 Recover Rotated Sorted Array C++ O(n) O(1) Easy 46 Majority Number C++ O(n) O(1) Easy LeetCode Tip 47 Majority Number II C++ O(n) O(1) Medium EPI 48 Majority Number III C++ O(n) O(k) Medium EPI 49 Sort Letters by Case C++ O(n) O(1) Medium Two Pointers 50 Product of Array Exclude Itself C++ O(n) O(1) Easy 51 Previous Permutation C++ O(n) O(1) Medium 52 Next Permutation C++ O(n) O(1) Medium LeetCode 57 3 Sum C++ O(n^2 ) O(1) Medium LeetCode Two Pointers, Sort 58 4 Sum C++ O(n^3 ) O(1) Medium LeetCode todo 59 3 Sum Closest C++ O(n^2 ) O(1) Medium LeetCode Two Pointers, Sort 64 Merge Sorted Array II C++ O(m+n) O(1) Easy LeetCode todo 100 Remove Duplicates from Sorted Array C++ O(n) O(1) Easy LeetCode Two Pointers 101 Remove Duplicates from Sorted Array II C++ O(n) O(1) Easy LeetCode Two Pointers 133 Longest Words C++ O(n) O(n) Easy 144 Interleaving Positive and Negative Numbers C++ O(n) O(1) Medium Two Pointers 161 Rotate Image C++ O(n^2 ) O(1) Medium LeetCode 162 Set Matrix Zeroes C++ _O(m*n)_ O(1) Medium LeetCode 172 Remove Element C++ O(n) O(1) Easy LeetCode Two Pointers 185 Matrix Zigzag Traversal C++ _O(m*n)_ O(1) Easy todo 189 First Missing Positive C++ O(n) O(1) Easy LeetCode, EPI Hash 190 Next Permutation II C++ O(n) O(1) Medium LeetCode 200 Longest Palindromic Substring C++ O(n) O(n) Medium LeetCode Manacher's Algorithm 363 Trapping Rain Water C++ O(n) O(1) Medium LeetCode Two Pointers, Tricky 373 Partition Array by Odd and Even C++ O(n) O(1) Easy Two Pointers 374 Spiral Matrix C++ _O(m*n)_ O(1) Medium LeetCode 381 Spiral Matrix II C++ O(n^2 ) O(1) Medium LeetCode todo 382 Triangle Count C++ O(n^2 ) O(1) Medium todo 383 Container With Most Water C++ O(n) O(1) Medium LeetCode, EPI Two Pointers 388 Permutation Sequence C++ O(n^2 ) O(n) Medium LeetCode 389 Valid Sudoku C++ O(9^2 ) O(9) Easy LeetCode 404 Subarray Sum II C++ O(nlogn) O(n) Hard todo 405 Submatrix Sum C++ _O(m*n^2 )_ O(m) Hard todo 406 Minimum Size Subarray Sum C++ O(n) O(1) Medium LeetCode Two Pointers, Binary Search 539 Move Zeroes C++ O(n) O(1) Easy LeetCode Two Pointers Backtracking PID# Title Source Time Space Difficulty Tag Note 15 Permutations C++ _O(n*n!)_ O(n) Medium LeetCode, EPI 16 Permutations II C++ _O(n*n!)_ O(n) Medium LeetCode, EPI 17 Subsets C++ _O(n*2^n )_ O(1) Medium LeetCode 18 Subsets II C++ _O(n*2^n )_ O(1) Medium LeetCode 33 N-Queens C++ _O(n*n!)_ O(n) Medium LeetCode, EPI 34 N-Queens II C++ _O(n*n!)_ O(n) Medium LeetCode, EPI 123 Word Search C++ O(mnl) O(l) Medium LeetCode todo 132 Word Search II C++ O(mnl) O(l) Hard Trie, DFS 135 Combination Sum C++ _O(k*n^k )_ O(k) Medium LeetCode DFS 136 Palindrome Partitioning C++ O(2^n ) O(n) Easy LeetCode, EPI 152 Combinations C++ _O(k*n^k )_ O(k) Medium LeetCode, EPI 153 Combination Sum II C++ _O(k*C(n,k))_ O(k) Medium LeetCode DFS 425 Letter Combinations of a Phone Number C++ _O(n*4^n )_ O(n) Medium LeetCode 426 Restore IP Addresses C++ O(1) O(1) Medium LeetCode 427 Generate Parentheses C++ O(4^n / n^(3/2) ) O(n) Medium LeetCode todo Binary Search PID# Title Source Time Space Difficulty Tag Note 14 First Position of Target C++ O(logn) O(1) Easy 28 Search a 2D Matrix C++ O(logm + logn) O(1) Easy LeetCode 60 Search Insert Position C++ O(logn) O(1) Easy LeetCode 61 Search for a Range C++ O(logn) O(1) Medium LeetCode 62 Search in Rotated Sorted Array C++ O(logn) O(1) Medium LeetCode 63 Search in Rotated Sorted Array II C++ O(logn) O(1) Medium LeetCode 65 Median of two Sorted Arrays C++ O(log(min(m,n))) O(1) Hard LeetCode, EPI todo 74 First Bad Version C++ O(logn) O(1) Medium 75 Find Peak Element C++ O(logn) O(1) Medium LeetCode 76 Longest Increasing Subsequence C++ O(nlogn) O(n) Medium CTCI 141 Sqrt(x) C++ O(logn) O(1) Easy LeetCode 159 Find Minimum in Rotated Sorted Array C++ O(logn) O(1) Medium LeetCode 160 Find Minimum in Rotated Sorted Array II C++ O(logn) O(1) Medium LeetCode 183 Wood Cut C++ O(nlogL) O(1) Medium 390 Find Peak Element II C++ Java O(m+n) O(1) Hard todo 437 Copy Books C++ O(nlogp) O(1) Hard UVa 714 todo Binary Search Trees PID# Title Source Time Space Difficulty Tag Note 11 Search Range in Binary Search Tree C++ O(n) O(h) Medium EPI 86 Binary Search Tree Iterator C++ O(1) O(h) Hard LeetCode 87 Remove Node in Binary Search Tree C++ O(h) O(h) Hard todo 249 Count of Smaller Number before itself C++ O(nlogn) O(n) Hard BST, BIT, Divide and Conquer, Merge Sort 360 Sliding Window Median C++ O(nlogw) O(w) Hard todo 391 Number of Airplanes in the Sky C++ O(nlogn) O(n) Easy BST, Heap 401 Kth Smallest Number in Sorted Matrix C++ O(klog(min(m,n,k))) O(min(m,n,k)) Medium BST, Heap Bit Manipulation PID# Title Source Time Space Difficulty Tag Note 1 A + B Problem C++ O(1) O(1) Medium 82 Single Number C++ O(n) O(1) Easy LeetCode 83 Single Number II C++ O(n) O(1) Easy LeetCode 84 Single Number III C++ O(n) O(1) Medium CTCI 142 O(1) Check Power of 2 C++ O(1) O(1) Easy 179 Update Bits C++ O(1) O(1) Medium CTCI 181 Flip Bits C++ O(1) O(1) Easy CTCI 196 Find the Missing Number C++ O(n) O(1) Medium 365 Count 1 in Binary C++ O(1) O(1) Easy CTCI Breadth-First Search PID# Title Source Time Space Difficulty Tag Note 69 Binary Tree Level Order Traversal C++ O(n) O(n) Medium LeetCode BFS 70 Binary Tree Level Order Traversal II C++ O(n) O(n) Medium LeetCode BFS 71 Binary Tree Zigzag Level Order Traversal C++ O(n) O(n) Medium LeetCode BFS 120 Word Ladder C++ _O(n*d)_ O(d) Medium LeetCode BFS 121 Word Ladder II C++ _O(n*d)_ O(d) Hard LeetCode todo 127 Topological Sorting C++ O(V+E) O(E) Medium todo 137 Clone Graph C++ O(V+E) O(V) Medium BFS 176 Route Between Two Nodes in Graph C++ O(n) O(n) Medium DFS, BFS 178 Graph Valid Tree C++ O(V+E) O(V+E) Medium LeetCode todo 431 Find the Connected Component in the Undirected Graph C++ O(n) O(n) Medium todo 477 Surrounded Regions C++ _O(m*n)_ O(m+n) Medium LeetCode Data Structure PID# Title Source Time Space Difficulty Tag Note 134 LRU Cache C++ O(1) O(k) Hard LeetCode, EPI List, Hash Depth-First Search PID# Title Source Time Space Difficulty Tag Note 90 K Sum II C++ _O(k*C(n,k))_ O(k) Medium 376 Binary Tree Path Sum C++ O(n) O(h) Easy LeetCode 433 Number of Islands C++ _O(m*n)_ _O(m*n)_ Easy LeetCode DFS 480 Binary Tree Paths C++ _O(n*h)_ O(h) Easy LeetCode Dynamic Programming PID# Title Source Time Space Difficulty Tag Note 20 Dices Sum C++ O(n^2 ) O(n) Hard todo 29 Interleaving String C++ _O(m*n)_ O(min(m,n)) Medium EPI 43 Maximum Subarray III C++ _O(k*n)_ _O(k*n)_ Hard 77 Longest Common Subsequence C++ _O(m*n)_ O(min(m,n)) Medium 79 Longest Common Substring C++ _O(m*n)_ O(min(m,n)) Medium 89 K Sum C++ O(knt) _O(n*t)_ Hard 91 Minimum Adjustment Cost C++ O(knt) O(k) Medium 92 Backpack C++ _O(m*n)_ O(m) Easy 107 Word Break C++ _O(n*l^2 )_ O(n) Medium LeetCode, EPI todo 108 Palindrome Partitioning II C++ O(n^2 ) O(n) Medium LeetCode, EPI 109 Triangle C++ O(n) O(n) Easy LeetCode, EPI 110 Minimum Path Sum C++ _O(m*n)_ O(min(m,n)) Easy LeetCode, EPI 111 Climbing Stairs C++ O(n) O(1) Easy LeetCode 115 Unique Paths II C++ _O(m*n)_ O(min(m,n)) Easy LeetCode, CTCI DP, Math 118 Distinct Subsequences C++ _O(m*n)_ O(m) Medium LeetCode todo 119 Edit Distance C++ _O(m*n)_ O(min(m,n)) Medium LeetCode, CTCI DP 125 Backpack II C++ _O(m*n)_ O(m) Medium 149 Best Time to Buy and Sell Stock C++ O(n) O(1) Medium LeetCode, EPI 150 Best Time to Buy and Sell Stock II C++ O(n) O(1) Medium LeetCode, EPI 151 Best Time to Buy and Sell Stock III C++ O(n) O(1) Medium LeetCode, EPI 154 Regular Expression Matching C++ _O(m*n)_ O(m) Hard LeetCode todo 168 Burst Balloons C++ O(n^3 ) O(n^2 ) Medium LeetCode todo 191 Maximum Product Subarray C++ O(n) O(1) Medium LeetCode 392 House Robber C++ O(n) O(1) Medium LeetCode 393 Best Time to Buy and Sell Stock IV C++ _O(k*n)_ O(k) Hard LeetCode, EPI 395 Coins in a Line II C++ O(n) O(1) Medium 396 Coins in a Line III C++ O(n^2 ) O(n) Hard todo 397 Longest Increasing Continuous subsequence C++ O(n) O(1) Easy todo 398 Longest Increasing Continuous subsequence II C++ _O(m*n)_ _O(m*n)_ Hard todo 403 Continuous Subarray Sum II C++ O(n) O(1) Medium EPI todo 430 Scramble String C++ O(n^4 ) O(n^3 ) Hard LeetCode todo 435 Post Office Problem C++ _O(k*n^2 )_ O(n) Hard PKU 1160 todo 436 Maximal Square C++ _O(m*n)_ O(n) Medium LeetCode todo 512 Decode Ways C++ O(n) O(1) Medium LeetCode todo 513 Perfect Squares C++ _O(n*sqrt(n))_ O(n) Medium LeetCode todo 514 Paint Fence C++ O(n) O(1) Easy LeetCode todo 515 Paint House C++ O(n) O(1) Medium LeetCode todo 516 Paint House II C++ _O(n*k)_ O(k) Hard LeetCode todo 534 House Robber II C++ O(n) O(1) Medium LeetCode todo 564 Backpack VI C++ _O(n*t)_ O(t) Medium Greedy PID# Title Source Time Space Difficulty Tag Note 41 Maximum Subarray C++ O(n) O(1) Easy LeetCode 42 Maximum Subarray II C++ O(n) O(n) Medium 44 Minimum Subarray C++ O(n) O(1) Easy 45 Maximum Subarray Difference C++ O(n) O(n) Medium 116 Jump Game C++ O(n) O(1) Medium LeetCode 117 Jump Game II C++ O(n) O(1) Medium LeetCode 182 Delete Digits C++ O(n) O(n) Medium 187 Gas Station C++ O(n) O(1) Easy LeetCode todo 192 Wildcard Matching C++ O(m+n) O(1) Hard LeetCode todo 402 Continuous Subarray Sum C++ O(n) O(1) Medium EPI 412 Candy C++ O(n) O(n) Hard LeetCode Greedy 552 Create Maximum Number C++ _O(k*(m+n+k))_ ~ _O(k*(m+n+k^2 ))_ O(m+n+k^2 ) Hard LeetCode todo Hash Tables PID# Title Source Time Space Difficulty Tag Note 56 2 Sum C++ O(n) O(n) Medium LeetCode 124 Longest Consecutive Sequence C++ O(n) O(n) Medium LeetCode, EPI 128 Hash Function C++ O(n) O(1) Easy 129 Rehashing C++ O(n) O(n) Medium 138 Subarray Sum C++ O(n) O(n) Easy 186 Max Points on a Line C++ O(n^2 ) O(n) Medium LeetCode 211 String Permutation C++ O(n) O(1) Easy todo 384 Longest Substring Without Repeating Characters C++ O(n) O(1) Medium LeetCode, EPI 386 Longest Substring with At Most K Distinct Characters C++ O(n) O(n) Medium todo 432 Find the Weak Connected Component in the Directed Graph C++ O(nlogn) O(n) Medium todo 434 Number of Islands II C++ O(k) O(k) Hard todo 488 Happy Number C++ O(k) O(k) Easy LeetCode 547 Intersection of Two Arrays C++ O(m+n) O(min(m,n)) Easy EPI, LeetCode Two Pointers, Binary Search 548 Intersection of Two Arrays II C++ O(m+n) O(min(m,n)) Easy EPI, LeetCode Two Pointers, Binary Search Heap PID# Title Source Time Space Difficulty Tag Note 4 Ugly Number II C++ O(n) O(1) Medium CTCI BST, Heap 81 Data Stream Median C++ O(nlogn) O(n) Hard EPI BST, Heap 130 Heapify C++ O(n) O(1) Medium 364 Trapping Rain Water II C++ O(mn(logm+logn)) _O(m*n)_ Hard todo 518 Super Ugly Number C++ _O(n*k)_ O(n+k) Medium LeetCode todo Linked List PID# Title Source Time Space Difficulty Tag Note 16 Merge Two Sorted Lists C++ O(n) O(1) Easy LeetCode, EPI 35 Reverse Linked List C++ O(n) O(1) Easy LeetCode, EPI 36 Reverse Linked List II C++ O(n) O(1) Medium LeetCode, EPI 96 Partition List C++ O(n) O(1) Easy LeetCode 98 Sort List C++ O(nlogn) O(logn) Medium LeetCode, EPI todo 99 Reorder List C++ O(n) O(1) Medium LeetCode 102 Linked List Cycle C++ O(n) O(1) Medium LeetCode 103 Linked List Cycle II C++ O(n) O(1) Hard LeetCode todo 104 Merge k Sorted Lists C++ _O(n*logk)_ _O(1)_ Medium LeetCode Heap, Divide and Conquer 105 Copy List with Random Pointer C++ O(n) O(1) Medium LeetCode 106 Convert Sorted List to Binary Search Tree C++ O(n) O(logn) Medium LeetCode, EPI todo 112 Remove Duplicates from Sorted List C++ O(n) O(1) Easy LeetCode, EPI 113 Remove Duplicates from Sorted List II C++ O(n) O(1) Medium LeetCode, EPI 166 Nth to Last Node in List C++ O(n) O(1) Easy LeetCode 167 Two Lists Sum C++ O(n) O(1) Easy LeetCode todo 170 Rotate List C++ O(n) O(1) Medium LeetCode 173 Insertion Sort List C++ O(n^2 ) O(1) Easy LeetCode 174 Remove Nth Node From End of List C++ O(n) O(1) Easy LeetCode 223 Palindrome Linked List C++ O(n) O(1) Medium LeetCode 372 Delete Node in the Middle of Singly Linked List C++ O(1) O(1) Easy CTCI 380 Intersection of Two Linked Lists C++ O(m+n) O(1) Easy LeetCode 450 Reverse Nodes in k-Group C++ O(n) O(1) Hard LeetCode 451 Swap Nodes in Pairs C++ O(n) O(1) Easy LeetCode 452 Remove Linked List Elements C++ O(n) O(1) Naive LeetCode 511 Swap Two Nodes in Linked List C++ O(n) O(1) Medium todo Math PID# Title Source Time Space Difficulty Tag Note 2 Trailing Zeros C++ O(1) O(1) Easy LeetCode 3 Digit Counts C++ O(1) O(1) Medium CTCI 114 Unique Paths C++ O(min(m,n)) O(1) Easy LeetCode, CTCI DP, Math 163 Unique Binary Search Trees C++ O(n) O(1) Medium CTCI DP, Math, Catalan Number 180 Binary Represention C++ O(1) O(1) Hard CTCI todo 197 Permutation Index C++ O(n^2 ) O(1) Easy 198 Permutation Index II C++ O(n^2 ) O(n) Medium todo 394 Coins in a Line C++ O(1) O(1) Easy 411 Gray Code C++ O(2^n ) O(1) Medium LeetCode todo 413 Reverse Integer C++ O(1) O(1) Medium LeetCode 414 Divide Two Integer C++ O(1) O(1) Medium LeetCode 418 Integer to Roman C++ O(n) O(1) Medium LeetCode todo 419 Roman to Integer C++ O(n) O(1) Medium LeetCode todo 428 Pow(x, n) C++ O(1) O(1) Medium LeetCode 445 Cosine Similarity C++ O(n) O(1) Easy 517 Ugly Number C++ O(1) O(1) Easy CTCI, LeetCode OO Design PID# Title Source Time Space Difficulty Tag Note 204 Singleton C++ O(1) O(1) Easy 208 Assignment Operator Overloading (C++ Only) C++ O(n) O(1) Medium 496 Toy Factory C++ O(1) O(1) Easy 497 Shape Factory C++ O(1) O(1) Easy 498 Parking Lot C++ O(nmk) O(nmk) Hard CTCI OO Design, Pimpl Idiom, Smart Pointer Queue PID# Title Source Time Space Difficulty Tag Note 362 Sliding Window Maximum C++ O(n) O(k) Hard EPI Deque, Tricky Recursion PID# Title Source Time Space Difficulty Tag Note 22 Flatten List C++ O(n) O(h) Easy 72 Construct Binary Tree from Inorder and Postorder Traversal C++ O(n) O(n) Medium LeetCode, EPI 73 Construct Binary Tree from Preorder and Inorder Traversal C++ O(n) O(n) Medium LeetCode, EPI 93 Balanced Binary Tree C++ O(n) O(h) Easy LeetCode 94 Binary Tree Maximum Path Sum C++ O(n) O(h) Medium LeetCode 95 Validate Binary Search Tree C++ O(n) O(h) Medium LeetCode 97 Maximum Depth of Binary Tree C++ O(n) O(h) Easy LeetCode 131 Building Outline C++ O(nlogn) O(n) Hard EPI Sort, BST 140 Fast Power C++ O(logn) O(1) Medium 155 Minimum Depth of Binary Tree C++ O(n) O(h) Easy LeetCode 164 Unique Binary Search Trees II C++ _O(n*4^n / n^(3/2) )_ O(n) Medium LeetCode 177 Convert Sorted Array to Binary Search Tree With Minimal Height C++ O(n) O(logn) Easy LeetCode 201 Segment Tree Build C++ O(n) O(h) Medium Segment Tree, BST 202 Segment Tree Query C++ O(h) O(h) Medium Segment Tree, BST 203 Segment Tree Modify C++ O(h) O(h) Medium Segment Tree, BST 205 Interval Minimum Number C++ build tree: O(n), query: (h) O(h) Hard Segment Tree, BST 206 Interval Sum C++ build tree: O(n), query: O(logn) O(n) Hard Segment Tree, BIT 207 Interval Sum II C++ build tree: O(n), query: O(logn), modify: O(logn) O(n) Hard Segment Tree, BIT 245 Subtree C++ _O(m*n)_ O(1) Easy Morris Traversal 247 Segment Tree Query II C++ O(h) O(h) Hard Segment Tree, BST 248 Count of Smaller Number C++ build tree: O(n), query: O(logn) O(h) Medium Segment Tree, BST 371 Print Numbers by Recursion C++ O(n) O(n) Medium 375 Clone Binary Tree C++ O(n) O(h) Easy 378 Convert Binary Search Tree to Doubly Linked List C++ O(n) O(h) Medium 439 Segment Tree Build II C++ O(n) O(h) Medium Segment Tree, BST 453 Flatten Binary Tree to Linked List C++ O(n) O(h) Easy LeetCode 469 Identical Binary Tree C++ O(n) O(h) Easy 532 Reverse Pairs C++ O(nlogn) O(n) Medium variant of Count of Smaller Number before itself BIT, Merge Sort 535 House Robber III C++ O(n) O(h) Medium LeetCode Sort PID# Title Source Time Space Difficulty Tag Note 5 Kth Largest Element C++ O(n) ~ O(n^2 ) O(1) Medium EPI Two Pointers, Quick Sort 80 Median C++ O(n) O(1) Easy EPI 139 Subarray Sum Closest C++ O(nlogn) O(n) Medium Sort 143 Sort Colors II C++ O(n) O(1) Medium 148 Sort Colors C++ O(n) O(1) Medium LeetCode 156 Merge Intervals C++ O(nlogn) O(1) Easy LeetCode, EPI 184 Largest Number C++ O(nlogn) O(1) Medium LeetCode 366 Fibonacci C++ O(n) O(1) Easy 379 Reorder array to construct the minimum number C++ O(nlogn) O(1) Medium LeetCode 387 The Smallest Difference C++ O(max(m,n) * log(min(m,n))) O(1) Medium Two Pointers, Binary Search 399 Nuts & Bolts Problem C++ O(nlogn) O(logn) Medium Quick Sort 400 Maximum Gap C++ O(n) O(n) Hard LeetCode Bucket Sort 463 Sort Integers C++ O(n^2 ) O(1) Easy Insertion Sort, Selection Sort, Bubble Sort 464 Sort Integers II C++ O(nlogn) O(n) Easy Merge Sort, Heap Sort, Quick Sort 507 Wiggle Sort II C++ O(n) on average O(1) Medium LeetCode Tri Partition 508 Wiggle Sort C++ O(n) O(1) Medium LeetCode Stack PID# Title Source Time Space Difficulty Tag Note 12 Min Stack C++ O(n) O(1) Medium LeetCode, EPI 40 Implement Queue by Two Stacks C++ O(1), amortized O(n) Medium EPI 66 Binary Tree Preorder Traversal C++ O(n) O(1) Easy LeetCode, EPI Morris Traversal 67 Binary Tree Inorder Traversal C++ O(n) O(1) Easy LeetCode, EPI Morris Traversal 68 Binary Tree Postorder Traversal C++ O(n) O(1) Easy LeetCode, EPI Morris Traversal 122 Largest Rectangle in Histogram C++ O(n) O(n) Hard LeetCode, EPI Ascending Stack 126 Max Tree C++ O(n) O(n) Hard Descending Stack 367 Expression Tree Build C++ O(n) O(n) Hard 368 Expression Evaluation C++ O(n) O(n) Hard 369 Convert Expression to Polish Notation C++ O(n) O(n) Hard 370 Convert Expression to Reverse Polish Notation C++ O(n) O(n) Hard 421 Simplify Path C++ O(n) O(n) Medium LeetCode 423 Valid Parentheses C++ O(n) O(n) Easy LeetCode 424 Evaluate Reverse Polish Notation C++ O(n) O(n) Medium LeetCode 473 Add and Search Word C++ O(min(n,h)) O(min(n,h) Medium LeetCode Trie 510 Maximal Rectangle C++ _O(m*n)_ O(n) Hard LeetCode Ascending Stack 528 Flatten Nested List Iterator C++ O(n) O(h) Medium LeetCode String PID# Title Source Time Space Difficulty Tag Note 13 strStr C++ O(n+k) O(k) Easy LeetCode KMP Algorithm 53 Reverse Words in a String C++ O(n) O(1) Easy LeetCode, EPI 54 String to Integer(atoi) C++ O(n) O(1) Hard LeetCode 55 Compare Strings C++ O(n) O(c) Easy 78 Longest Common Prefix C++ O(n) O(1) Medium 157 Unique Characters C++ O(n) O(1) Easy CTCI 158 Two Strings Are Anagrams C++ O(n) O(1) Easy 171 Anagrams C++ _O(n*klogk)_ O(m) Easy LeetCode, EPI 212 Space Replacement C++ O(n) O(1) Easy 407 Plus One C++ O(n) O(1) Easy LeetCode 408 Add Binary C++ O(n) O(1) Easy LeetCode 415 Valid Palindrome C++ O(n) O(1) Easy LeetCode 417 Valid Number C++ O(n) O(1) Hard LeetCode Automata 420 Count and Say C++ _O(n*2^n )_ O(2^n ) Easy LeetCode 422 Length of Last Word C++ O(n) O(1) Easy LeetCode 524 Left Pad C++ O(p+n) O(1) Easy LeetCode System Design PID# Title Source Time Space Difficulty Tag Note 501 Mini Twitter C++ O(klogu) O(t+f) Medium Tree PID# Title Source Time Space Difficulty Tag Note 7 Binary Tree Serialization C++ O(n) O(h) Medium 85 Insert Node in a Binary Search Tree C++ O(h) O(1) Easy 88 Lowest Common Ancestor C++ O(n) O(h) Medium EPI 175 Invert Binary Tree C++ O(n) O(h) Easy LeetCode 442 Implement Trie C++ O(n) O(1) Medium LeetCode Trie