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) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        int solution = A[0];
        for (int i=1;i<n;++i){
            solution = solution^A[i];
        }
        return solution;
    }
};