leetcode ：Single Number

题目描述：
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?
代码如下：
运用了异或的运算，即相同取0，相异取1class Solution {

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

};