leedcode—— 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?

思路：

由于相同值异或结果为0,0和非零数异或结果为数本身。

序列：2 3 3 7 4 4 5 5 7

2^3 = 1

1^3 = 2

2^7 = 5

5^4 = 1

1^4 = 5

5^5=0

0^5=5

5^7=2

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