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.

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