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?

利用异或的性质：

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