Leetcode 136. Single Number

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?

s思路：
1. 这道题遇到过! 不用内存，那就是一直做xor运算，相同的数xor等于0，最后只剩下the single number.
2. 这道题就是利用两个数异或的性质，基本也就是一道数学题！

class Solution {
public:
    int singleNumber(vector<int>& nums) {

        int res=0;
        for(int i=0;i<nums.size();i++){
            res^=nums[i];    
        }
        return res;
    }
};