Leetcode Single Number

Description: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?

Solution:运用公式a^a=0, a^0=a。 

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