Single Number I

来源：Leetcode

原帖：http://oj.leetcode.com/problems/single-number/

题目：
Given an array of integers, every element appears twice except for one. Find that single one. Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

代码：

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