题目描述：

Given an 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?

代码实现：

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int ret = 0;
        for(int num:nums){
            ret^=num;
        }
        return ret;
    }
};