Leetcode 136 Single Number

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?

找到出现一次的数，开始自己的思路是先排下序，然后再遍历一遍，后来看到了别人的解答，好赞啊，利用异或满足结合律的性质，代码如下：

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int result = 0 ;  
        for (int i=0; i<nums.size(); i++)  
        {  
            result ^= nums[i];  
        }  
        return result;  
    }
};