[LeetCode] 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?

异或即可处理，而且，不仅能处理两次的情况，只要出现偶数次，都可以清零。

class Solution {
public:
    int singleNumber(int A[], int n) {
        
        int res = 0;
        
        for(int i = 0; i<n; i++)
        {
            res = res ^ A[i];
        }
        
        return res;
    }
};