[LeetCode]Find the Duplicate Number

这个题之前做过，实在没想出什么好方法，今天突然发现这个完全就是个有环链表找开始进入环的题目，真是相当精巧

public class Solution {
    public int findDuplicate(int[] nums) {
        int slow = 0;
        int fast = 0;
        do {
            slow = nums[slow];
            fast = nums[nums[fast]];
        } while (slow != fast);
        slow = 0;
        while (slow != fast) {
            slow = nums[slow];
            fast = nums[fast];
        }
        return slow;
    }
}