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 ans=A[0];        for(int i=1;i<n;i++) {            ans = ans^A[i];        }        return ans;    }};

Single Number