Jackson.tmm

LeetCode 1679 - Max Number of K-Sum Pairs You are given an integer array nums and an integer k. In one operation, you can pick two numbers from the array whose sum equals k and remove them from the array. Return the maximum number of operations you can perform on the array. example Input: nums = [1,2,3,4], k = 5 Output: 2 Explanation: Starting with nums = [1,2,3,4]: - Remove

LeetCode 581 - Shortest Unsorted Continuous Subarray Given an integer array nums, you need to find one continuous subarray that if you only sort this subarray in ascending order, then the whole array will be sorted in ascending order. Return the shortest such subarray and output its length. example: Input: nums = [2,6,4,8,10,9,15] Output: 5 Explanation: You need to sort [6, 4, 8, 10, 9] in ascending order to make

LeetCode 905 - Sort Array By Parity Given an integer array nums, move all the even integers at the beginning of the array followed by all the odd integers. Return any array that satisfies this condition. example: Input: nums = [3,1,2,4] Output: [2,4,3,1] Explanation: The outputs [4,2,3,1], [2,4,1,3], and [4,2,1,3] would also be accepted. Input: nums = [0] Output: [0] How can we solve this problem? 這個問題

LeetCode 844 - Backspace String Compare Given two strings s and t, return true if they are equal when both are typed into empty text editors. '#' means a backspace character. Note that after backspacing an empty text, the text will continue empty. example: Input: s = "ab#c", t = "ad#c" Output: true Explanation: Both s and t become "ac". Input: s = "ab##", t = "c#d#" Output: true Explanation:

LeetCode 669 - Trim a Binary Search Tree Given the root of a binary search tree and the lowest and highest boundaries as low and high, trim the tree so that all its elements lies in [low, high]. Trimming the tree should not change the relative structure of the elements that will remain in the tree (i.e., any node’s descendant should remain a descendant). It can be proven that there

LeetCode 700 - Search in a Binary Search Tree You are given the root of a binary search tree (BST) and an integer val. Find the node in the BST that the node’s value equals val and return the subtree rooted with that node. If such a node does not exist, return null. example Input: root = [4,2,7,1,3], val = 2 Output: [2,1,3] Input: root = [4,2,7,1,3], val = 5

LeetCode 1260 - Shift 2D Grid Given a 2D grid of size m x n and an integer k. You need to shift the grid k times. In one shift operation: Element at grid[i][j] moves to grid[i][j + 1]. Element at grid[i][n - 1] moves to grid[i + 1][0]. Element at grid[m - 1][n - 1] moves to grid[0][0]. Return the 2D grid after applying shift operation k times. example

LeetCode 59 - Spiral Matrix II Given a positive integer n, generate an n x n matrix filled with elements from 1 to n2 in spiral order. example Input: n = 3 Output: [[1,2,3],[8,9,4],[7,6,5]] Input: n = 1 Output: [[1]] How can we solve this problem? 這題跟Spiral Matrix做法差不多，我們不

LeetCode 289 - Game of Life According to Wikipedia’s article: “The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970.” The board is made up of an m x n grid of cells, where each cell has an initial state: live (represented by a 1) or dead (represented by a 0). Each cell interacts with its eight

LeetCode 682 - Baseball Game You are keeping score for a baseball game with strange rules. The game consists of several rounds, where the scores of past rounds may affect future rounds’ scores. At the beginning of the game, you start with an empty record. You are given a list of strings ops, where ops[i] is the ith operation you must apply to the record and is one of the