Given a **non-empty** array of integers `nums`, every element appears twice except for one. Find that single one.
You must implement a solution with a linear runtime complexity and use only constant extra space.
Example 1
Input:nums = [2,2,1]
Output:1
Example 2
Input:nums = [4,1,2,1,2]
Output:4
Example 3
Input:nums = [1]
Output:1
Constraints
- 1 <= nums.length <= 3 * 10^4
- -3 * 10^4 <= nums[i] <= 3 * 10^4
- Each element in the array appears twice except for one element which appears only once.