FIND THE DUPLICATE NUMBER LEETCODE SOLUTION C++

Given an array of integers nums containing n + 1 integers where each integer is in the range [1, n] inclusive.

There is only one repeated number in nums, return this repeated number.

You must solve the problem without modifying the array nums and uses only constant extra space.

Example 1:

Input: nums = [1,3,4,2,2]
Output: 2
Example 2:

Input: nums = [3,1,3,4,2]
Output: 3

Constraints:

1 <= n <= 105
nums.length == n + 1
1 <= nums[i] <= n
All the integers in nums appear only once except for precisely one integer which appears two or more times.

C++ SOLUTION :

class Solution {
public:
    int findDuplicate(vector<int>& nums)//LINKED LIST CYCLE METHOD 
     {
        int slow = nums[0];
        int fast = nums[0];
        do {
            slow = nums[slow];
            fast = nums[nums[fast]];
        } while (slow != fast);
        // Find the "entrance" to the cycle.
        slow = nums[0];
        while (slow != fast) // WHENEVER  2ND TYM FAST AND SLOW POINTER MEETS IT GIVES DUPLICATE NUMBER  (EITHER THE FAST OR SLOW )
        {
            slow = nums[slow];
            fast = nums[fast];
        }
        return slow;
    }

};