Stay button algorithm --136SingleNumber [E]

Given a non-empty array of integers, every element appears twice except for one. Find that single one.

Note:

Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

Example 1:

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

Example 2:

INPUT: [4,1,2,1,2] 
the Output:. 4 


Solution: 
　　using the XOR operation, the same is 0, 1 is different, the remaining number that is unique to that

1 class Solution {
2 public:
3     int singleNumber(vector<int>& nums) {
4         int res = 0;
5         for (auto a : nums)res = res ^ a;
6         return res;
7     }
8 };