136. Single Number

1. 问题描述
   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?

2. 解决思路
   智力题，这里用抑或相加即可。

3. 代码

class Solution {public:    int singleNumber(vector<int>& nums) {        for (int i = 1; i <  nums.size(); ++i) {            nums[0] ^= nums[i];        }        return nums[0];    }};