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.
1 <= nums.length <= 3 * 10^4-3 * 10^4 <= nums[i] <= 3 * 10^4nums = [2,2,1]1nums = [4,1,2,1,2]4nums = [1]1