LintCode-劍指Offer-(82)落單的數

class Solution {
public:
    /**
     * @param A: Array of integers.
     * return: The single number.
     */
    int singleNumber(vector<int> &A) {
        // write your code here
        int n=0;
        for(int i=0;i<A.size();i++){
            n=n^A[i];
        }
        return n;
    }
};