[LeetCode] Single Number

题目：

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?

解答：

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

没什么可多说的，用到的知识点就是：a异或a = 0，a异或0 = a，异或满足交换律