670. 最大交换 给定一个非负整数,你至多可以交换一次数字中的任意两位.返回你能得到的最大值. 示例 1 : 输入: 2736 输出: 7236 解释: 交换数字2和数字7. 示例 2 : 输入: 9973 输出: 9973 解释: 不需要交换. 注意: 给定数字的范围是 [0, 108] class Solution { public int maximumSwap(int num) { if(num<10) return num; int[] nums = new int[9]; int…

最大交换 给定一个非负整数,你至多可以交换一次数字中的任意两位.返回你能得到的最大值. 示例 1 : 输入: 2736 输出: 7236 解释: 交换数字2和数字7. 示例 2 : 输入: 9973 输出: 9973 解释: 不需要交换. 注意: 给定数字的范围是 [0, 108] 思路 class Solution { public int maximumSwap(int num) { char[] A = Integer.toString(num).toCharArray(); int[]…

The set [1,2,3,…,n] contains a total of n! unique permutations. By listing and labeling all of the permutations in order, We get the following sequence (ie, for n = 3): "123" "132" "213" "231" "312" "…

Implement wildcard pattern matching with support for '?' and '*'. '?' Matches any single character. '*' Matches any sequence of characters (including the empty sequence). The matching should cover the entire input string (not partial). The function p…

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…

Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by…