Single Number

Given an array of integers, every element appears twice except for one. Find that single one.

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

 按位与同一个数两次。