Duplicate_Number.java

/*

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 using 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
Example 3:

Input: nums = [3,3,3,3,3]
Output: 3


*/


class Duplicate_Number {
    public int findDuplicate(int[]  nums) {

        int slow = nums[0];
        int fast = nums[0];

        while (true) {
            slow = nums[slow];
            fast = nums[nums[fast]];
            if(slow == fast){
                break;
            }
        }

        slow = nums[0];

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

        return slow;
    }
}