duplicateNumber.cpp

//6th
//Find the Duplicate Number
// 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


//Rabit and tortoise method.

class Solution {
public:
    int findDuplicate(vector<int>& nums) {
        int slow = nums[0];
        int fast = nums[0];
        do{
            slow = nums[slow];
            fast = nums[nums[fast]];
        }while(slow!=fast);

        fast = nums[0];
    while(slow != fast){
        slow = nums[slow];
        fast = nums[fast];
    }
        return slow;
    }


};