题目：

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?

这题目的要求不仅是要求是线性时间，希望也不会使用额外的内存，那么也就是你无法运用其他的数据结构。也是参考了其他人的答案。对于位操作的特性还有待进一步挖掘。

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

【LeetCode】136. Single Number 解题小结