题目描述：
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?
解题方案：
该题利用异或可以方便求解，下面本题是代码：
1 class Solution { 2 public: 3 int singleNumber(int A[], int n) { 4 int result = A[0]; 5 for(int i = 1; i < n; ++i){ 6 //利用异或 7 result = result ^ A[i]; 8 } 9 return result; 10 } 11 };
原文：http://www.cnblogs.com/skycore/p/4001092.html