[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?

class Solution {
public:
    int singleNumber(int A[], int n) {
        int ret = A[0];
        for(int i=1; i<n; i++)
        {
            ret = ret ^ A[i];
        }
        return ret;
    }
};