Single Number

Easy

Given a non-empty array nums where every element appears twice except one, find that single one. Do it with O(n) time and O(1) extra space.

Example 1

Input:  nums = [2,2,1]
Output: 1

Example 2

Input:  nums = [4,1,2,1,2]
Output: 4

Constraints

• 1 <= nums.length <= 3*10^4
• Each element appears twice except one.