Given an array of integers
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.
Input: nums = [1,3,4,2,2] Output: 2
Input: nums = [3,1,3,4,2] Output: 3
Input: nums = [1,1] Output: 1
Input: nums = [1,1,2] Output: 1
1 <= n <= 105
nums.length == n + 1
1 <= nums[i] <= n
numsappear only once except for precisely one integer which appears two or more times.