389. 找不同 给定两个字符串 s 和 t,它们只包含小写字母. 字符串 t 由字符串 s 随机重排,然后在随机位置添加一个字母. 请找出在 t 中被添加的字母. 示例: 输入: s = "abcd" t = "abcde" 输出: e 解释: 'e' 是那个被添加的字母. class Solution { // public char findTheDifference(String s, String t) { // char res = t.charAt(t…

719. 找出第 k 小的距离对 给定一个整数数组,返回所有数对之间的第 k 个最小距离.一对 (A, B) 的距离被定义为 A 和 B 之间的绝对差值. 示例 1: 输入: nums = [1,3,1] k = 1 输出:0 解释: 所有数对如下: (1,3) -> 2 (1,1) -> 0 (3,1) -> 2 因此第 1 个最小距离的数对是 (1,1),它们之间的距离为 0. 提示: 2 <= len(nums) <= 10000. 0 <= nums[i] &l…

513. 找树左下角的值 给定一个二叉树,在树的最后一行找到最左边的值. 示例 1: 输入: 2 / \ 1 3 输出: 1 示例 2: 输入: 1 / \ 2 3 / / \ 4 5 6 / 7 输出: 7 注意: 您可以假设树(即给定的根节点)不为 NULL. /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * Tr…

1. 题目 2. 解答 2.1. 方法一 将 s 和 t 转化为 Python 的列表,然后遍历列表 s 的元素,将它们从列表 t 中删除,最后列表 t 中会余下一个元素,即为所求. class Solution: def findTheDifference(self, s, t): """ :type s: str :type t: str :rtype: str """ s_list = list(s) t_list = list(t) fo…

389.找不同 知识点:哈希表.抵消思想: 题目描述 给定两个字符串 s 和 t,它们只包含小写字母. 字符串 t 由字符串 s 随机重排,然后在随机位置添加一个字母. 请找出在 t 中被添加的字母. 示例 输入:s='abcdac'; t='adaccbb'; 输出:'b'; 解释:因为b是被添加的元素,不一定在最后位置: 解法一:数组型哈希表: 这道题目可以用哈希表去做,采用数组型哈希表:数组本身就是一个哈希表:其索引作为一个key,其值作为value:方法如下:可以将26个字母作为key,…

Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers. Ensure that numbers within the set are sorted in ascending order. Example 1…

Given a string S, you are allowed to convert it to a palindrome by adding characters in front of it. Find and return the shortest palindrome you can find by performing this transformation. For example: Given "aacecaaa", return "aaacecaaa&qu…

Given a 2D board and a list of words from the dictionary, find all words in the board. Each word must be constructed from letters of sequentially adjacent cell, where "adjacent" cells are those horizontally or vertically neighboring. The same le…

Design a data structure that supports the following two operations: void addWord(word)bool search(word) search(word) can search a literal word or a regular expression string containing only letters a-z or .. A . means it can represent any one letter.…

There are a total of n courses you have to take, labeled from 0 to n - 1. Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1] Given the total number of courses and a l…