Find Duplicate in Array

Given an array nums containing n + 1 integers each in [1, n], there is exactly one duplicate number. Find it without modifying the array and using only constant extra space.

Examples
Input: [1,3,4,2,2]
Output: 2
Hints

Find Duplicate in Array

Given an array nums containing n + 1 integers each in [1, n], there is exactly one duplicate number. Find it without modifying the array and using only constant extra space.