Leetcode

2. Add Two Numbers: 难度简单，利用了数字相加的进位的原理。 1028. Conver to Base - 2: 难度中等，进位原理。 1030. Next Greater Node In Linked List: 难度简单，使用栈。 1020. Number of Enclaves: 难度中等，可以用图的算法，但是用遍历更简单。 83. Remove Duplicates from Sorted List: 难度简单，链表。 82. Remove Duplicates from Sorted List II:难度简单，需要引入一个前置节点。 559. Maximum Depth of N-ary Tree: 难度简单，动态规划。 198. House Robber: 难度简单，动态规划，利用循环将最优解传递。 213. House Robber ii: 难度简单，动态规划，利用循环将最优解传递。 [509. Fibonacci Number]: 难度简单，斐波那契数列。 [307. Range Sum Query - Mutable]：Easy。 [1025. Divisor Game]: 难度中等，动态规划求解。 [1026. Maximum Difference Between Node and Ancestor]: 难度简单，动态规划求解。 [1027. Longest Arithmetic Sequence]: 难度中等，动态规划。 [1028. Recover a Tree From Preorder Traversal]: 难度中等，使用depth和ArrayBuffer[TreeNode]来存储中间计算结果。 234. Palindrome Linked List: 难度简单。 203. Remove Linked List Elements: 难度简单。 160. Intersection of Two Linked Lists: 难度简单。 700. Search in a Binary Search Tree: 难度简单。 617. Merge Two Binary Trees: 难度中等，递归思想。 350. Intersection of Two Arrays II: 难度简单。 704. Binary Search: 难度简单，二分查找。 744. Find Smallest Letter Greater Than Target: 难度简单，二分查找。 367. Valid Perfect Square: 难度简单，采用Long处理。 877. Stone Game: 难度中等,动态规划，使用矩阵的思想来做动态规划，是一个不错的思路。 931. Minimum Falling Path Sum: 难度中等，动态规划，知道上一题的矩阵解法，做这个也比较简单了。 983. Minimum Cost For Tickets: 难度简单，动态规划，从后往前的来考虑。 1030. Matrix Cells in Distance Order: 难度简单，使用广度遍历，竟然忘记广度遍历怎么写了。。。。BFS use Queue，DFS use Stack。。。 1029. Two City Scheduling: 难度简单，需要用点数学推导。 1031. Maximum Sum of Two Non-Overlapping Subarrays: 难度简单，但是过程的代码量可能要多一些。。。 1032. Stream of Characters: 难度简单，很容易就想到的方法。。。 374. Guess Number Higher or Lower: 难度简单，二分查找。 441. Arranging Coins: 难度简单，二分查找，找最近的那一个。 475. Heaters: 难度简单，遍历做二分查找，很傻的题目。 69. Sqrt(x): 难度简单，遍历做二分查找，最近值。 278. First Bad Version: 难度简单，同上。 981. Time Based Key-Value Store: 难度简单，偷懒用了跳表结构。 647. Palindromic Substrings: Hard，使用Manacher算法。 413. Arithmetic Slices: Easy，很简单的优化。 [1033. Moving Stones Until Consecutive]: 难度简单。 714. Best Time to Buy and Sell Stock with Transaction Fee: Hard，这个动态规划的点很难想到。 413. Arithmetic Slices: Easy，很简单的优化。 1034. Coloring A Border: Easy，BFS。 1035. Uncrossed Lines: Hard，动态规划，使用矩阵的方式。。第二次了。。 771. Jewels and Stones: Easy。 1103. Distribute Candies to People: Easy。 1104. Path In Zigzag Labelled Binary Tree: 比较有意思的一道题。 1093. Statistics from a Large Sample: Easy. 1094. Car Pooling: Easy. 1124. Longest Well-Performing Interval: Medium，采用简单的动态规划。 1122. Relative Sort Array: Easy。 1137. N-th Tribonacci Number: Easy。 1138. Alphabet Board Path: Easy。 1139. Largest 1-Bordered Square: Medium，很繁琐的一系列操作。 1144. Decrease Elements To Make Array Zigzag: Medium。 1145. Binary Tree Coloring Game: Medium，一次过。 491. Increasing Subsequences: Medium. 11. Container With Most Water: Easy. 15. 3Sum: Easy. 136. Single Number: Too easy. 796. Rotate String: Easy 50. Pow(x, n): Easy 337. House Robber III: Easy. 825. Friends Of Appropriate Ages: Easy. 701. Insert into a Binary Search Tree: Easy. 933. Number of Recent Calls: Easy. 1047. Remove All Adjacent Duplicates In String: Easy. 844. Backspace String Compare: Easy. 451. Sort Characters By Frequency: Easy. 43. Multiply Strings: Medium. 869. Reordered Power of 2: Medium. [870. Advantage Shuffle](870. Advantage Shuffle): Medium. 121. Best Time to Buy and Sell Stock： Easy. 122. Best Time to Buy and Sell Stock II: Easy. 503. Next Greater Element II： Medium. 168. Excel Sheet Column Title: Easy. 830. Positions of Large Groups: Easy. 101. Symmetric Tree: Easy. 78. Subsets: Easy. 207. Course Schedule: Medium，差点使用连通图，结果不是，用 stack 实现dfs。 257. Binary Tree Paths: Easy. 16. 3Sum Closest: Easy. 129. Sum Root to Leaf Numbers: Easy. 238. Product of Array Except Self: Easy. 686. Repeated String Match: Easy. 888. Fair Candy Swap: Easy. 1154. Day of the Year: Easy. 1155. Number of Dice Rolls With Target Sum: Medium，做个缓存. 1156. Swap For Longest Repeated Character Substring: Medium. 1002. Find Common Characters: Easy. 576. Out of Boundary Paths: Easy. 169. Majority Element: Easy. 229. Majority Element II: Easy. 1080. Insufficient Nodes in Root to Leaf Paths: Medium. 1146. Snapshot Array: Medium. 976. Largest Perimeter Triangle: Medium，要先做排序，还没想到。 693. Binary Number with Alternating Bits: Easy. 779. K-th Symbol in Grammar: Medium，开始的想法想错了。 905. Sort Array By Parity: Easy. 482. License Key Formatting: Easy. 3. Longest Substring Without Repeating Characters: Not too medium. 5. Longest Palindromic Substring: Easy. 17. Letter Combinations of a Phone Number: Easy. 19. Remove Nth Node From End of List: Easy. 22. Generate Parentheses: Medium. 98. Validate Binary Search Tree: Medium. 152. Maximum Product Subarray: Easy. 31. Next Permutation: Medium. 322. Coin Change: Medium. 142. Linked List Cycle II: Medium. 33. Search in Rotated Sorted Array: Easy. 102. Binary Tree Level Order Traversal: Easy. 34. Find First and Last Position of Element in Sorted Array: Easy. 139. Word Break: Medium. 208. Implement Trie (Prefix Tree): Medium. 这里实现的 Trie Tree 性能太差，如果以单个字母来实现，性能简直是差的可以。 114. Flatten Binary Tree to Linked List: Medium. 96. Unique Binary Search Trees: Medium. 94. Binary Tree Inorder Traversal: Easy. 1162. As Far from Land as Possible: Easy. Use dp. 1160. Find Words That Can Be Formed by Characters: Easy. 1161. Maximum Level Sum of a Binary Tree: Easy. 1175. Prime Arrangements: Easy. 1332. Remove Palindromic Subsequences: Easy. 1333. Filter Restaurants by Vegan-Friendly, Price and Distance: Easy. 1334. Find the City With the Smallest Number of Neighbors at a Threshold Distance: Floyd-Warshall Algorithm to find shortest path between cities. 1341. The K Weakest Rows in a Matrix: Easy. 1342. Reduce Array Size to The Half: Easy. 1343. Maximum Product of Splitted Binary Tree: Easy.