LeetCode 136 Single Number 数组中除一个数外其他数都出现两次，找出只出现一次的数

Given an array of integers, every element appears twice except for one. Find that single one.

 1 class Solution {
 2 public:
 3     int singleNumber(vector<int>& nums) {
 4         int size=nums.size();
 5         if(size==0||nums.empty())
 6             return 0;
 7         int res=0;
 8         for(int i=0;i<size;++i)
 9             res^=nums[i];
10         return res;
11     }
12 };