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 分析 难度 中 来源 https://leetcode.com/problems/find-the-duplicate-number/ 题目 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] Output: 2 Example 2: Input: [3,1,3,4,2] Output: 3 Note: You must not modify the array (assume the array is read only). You must use only constant, O(1) extra space. Your runtime complexity should be less than O(n2). There is only one duplicate number in the array, but it could be repeated more than once. 解答  1 package LeetCode; 2 3 public class L287_FindTheDuplicateNumber { 4 public int findDuplicate(int[] nums) { 5 int slow=nums[0]; 6 int fast=nums[nums[0]]; 7 while(slow!=fast){ 8 slow=nums[slow]; 9 fast=nums[nums[fast]]; 10 } 11 int slow2=0; 12 while(slow2!=slow){ 13 slow=nums[slow]; 14 slow2=nums[slow2]; 15 } 16 return slow; 17 } 18 public static void main(String[] args){ 19 L287_FindTheDuplicateNumber l287=new L287_FindTheDuplicateNumber(); 20 int[] nums={3,1,3,4,2}; 21 System.out.println(l287.findDuplicate(nums)); 22 } 23 }     posted on 2018-11-08 15:27  flowingfog  阅读(57)  评论(0)  编辑  收藏