Leetcode 136. Single Number

原题：
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?

解决方法：
a^a=0, a^0=a.所以讲所以数异或即可得答案。

代码：

int singleNumber(vector<int>& nums) {
int res = 0;
for(auto num: nums)
res ^= num;
return res;
}