LeetCode:60. Permutation Sequence,n全排列的第k个子列 : 题目: LeetCode:60. Permutation Sequence 描述: 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…

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80. Remove Duplicates from Sorted Array II Follow up for "Remove Duplicates":What if duplicates are allowed at most twice? For example,Given sorted array nums = [1,1,1,2,2,3], Your function should return length = 5, with the first five elements…

题目 Follow up for "Remove Duplicates": What if duplicates are allowed at most twice? For example, Given sorted array nums = [1,1,1,2,2,3], Your function should return length = 5, with the first five elements of nums being 1, 1, 2, 2 and 3. It doe…

1. 原题链接 https://leetcode.com/problems/permutation-sequence/description/ 2. 题目要求 给出整数 n和 k ,k代表从1到n的整数所有排列序列中的第k个序列,返回String类型的第k个序列 3. 解题思路 首先我们要知道这个序列是按照什么规律排列下去的,假如此时n=4,k= 21,n=4时所有的排列如下: 可以看出 n=4 时,一共有 4!=24种排列组合. 每一个数字开头各有 6 种排列组合,因此我们可以把同一数字开头的…

Implement atoi to convert a string to an integer. Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases. Notes: It is intended for this problem to be spe…

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" "3…

第一题:题目内容 Given an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each input would have exactly one solution, and you may not use the same element twice. Example: Given nums = [2, 7…

60. 第k个排列 给出集合 [1,2,3,-,n],其所有元素共有 n! 种排列. 按大小顺序列出所有排列情况,并一一标记,当 n = 3 时, 所有排列如下: "123" "132" "213" "231" "312" "321" 给定 n 和 k,返回第 k 个排列. 说明: 给定 n 的范围是 [1, 9]. 给定 k 的范围是[1, n!]. 示例 1: 输入: n = 3,…

80. 删除有序数组中的重复项 II 知识点:数组:排序:双指针: 题目描述 给你一个有序数组 nums ,请你 原地 删除重复出现的元素,使每个元素 最多出现两次 ,返回删除后数组的新长度. 不要使用额外的数组空间,你必须在 原地 修改输入数组 并在使用 O(1) 额外空间的条件下完成. 示例 输入:nums = [1,1,1,2,2,3] 输出:5, nums = [1,1,2,2,3] 解释:函数应返回新长度 length = 5, 并且原数组的前五个元素被修改为 1, 1, 2, 2,…