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

异或运算实现。