[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?

这道题是不难的，其实只要想到如果去利用重复数均为2的特点就可以了，方法就是——异或！！！

此题是LeetCode中AC率暂时最高的一题。

代码如下：

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;
    }
};