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：

 1 class Solution {
 2 public:
 3     int singleNumber(vector<int>& nums) {
 4         int result = 0 ;  
 5         for (int i=0; i<nums.size(); i++)  
 6         {  
 7             result ^= nums[i];  
 8         }  
 9         return result;  
10     }
11 };