leetcode287

public class Solution {
    public int FindDuplicate(int[] nums) {
        if (nums.Count() > )
            {
                int slow = nums[];
                int fast = nums[nums[]];
                while (slow != fast)
                {
                    slow = nums[slow];
                    fast = nums[nums[fast]];
                }

                fast = ;
                while (fast != slow)
                {
                    fast = nums[fast];
                    slow = nums[slow];
                }
                return slow;
            }
            return -;
    }
}

https://leetcode.com/problems/find-the-duplicate-number/#/description