[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 i,sum=0;for( i=0;i<=n-1;i++){sum=sum^A[i];}return sum;            }};