Level:   Medium 题目描述: Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that there is only one duplicate number, find the duplicate one. Exampl…

题意: 有一个含有n+1个元素的数组,元素值是在1-n之间的整数,请找出其中出现超过1次的数.(保证仅有1个出现次数是超过1的数) 思路: 方法一:O(nlogn).根据鸽笼原理及题意,每次如果<=k的数超过了k个,那么答案必定在[1,k].可以用二分枚举答案来解决. bool left(vector<int>& nums,int tar)//是否在左边 { ; ; i<nums.size(); i++) if(nums[i]<=tar) cnt++; return…

Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that there is only one duplicate number, find the duplicate one. Note: You must not modify th…

［抄题］: Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that there is only one duplicate number, find the duplicate one. Example 1: Input: [1,3…

对于一个长度为n+1的数组,其中每一个值的取值范围是[1,n],可以证明的是必然存在一个重复数字(抽屉原理),假设仅存在一个重复数字,找到他. 举例:输入:[1,3,4,2,1],输出:1 自己做的时候,要么时间复杂度到o(n2),要么需要额外的存储空间利用hashset,下面来分析一下leetcode上别人的算法吧. 方法一:通过图论中环的有关知识解决 public int findDuplicate(int[] nums) { // Find the intersection point o…

Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate element must exist. Assume that there is only one duplicate number, find the duplicate one. Note: You must not modify t…

最容易想到的思路是新开一个长度为n的全零list p[1~n].依次从nums里读出数据,假设读出的是4, 就将p[4]从零改成1.如果发现已经是1了,那么这个4就已经出现过了,所以他就是重复的那个数.这个解法的时间复杂度是O(N).但是由于本题要求空间复杂度是O(1).所以不能用. 可以用二分法,low = 1, high = n, mid = (left + right)//2,如果<=mid 的元素个数 > mid,那么重复的数字一定在[1, mid]区间内.反之,则一定在[mid+1,…

Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that there is only one duplicate number, find the duplicate one. Example 1: Input: [1,3,4,2,2…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 保存已经访问过的数字 链表成环 二分查找 日期 题目地址:https://leetcode.com/problems/find-the-duplicate-number/description/ 题目描述 Given an array nums containing n + 1 integers where each integer is betwe…

Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that there is only one duplicate number, find the duplicate one. Note: You must not modify th…