Given a non-empty 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?

Example 1:

Input: [2,2,1]
Output: 1

Example 2:

Input: [4,1,2,1,2]
Output: 4

题意

找出一个非空数组中只出现一次的数字，除了这个数，其他数都出现了两次。

思路

位运算。
相同的数异或为0，一个数异或0为它本身。

代码

class Solution:
    def singleNumber(self, nums):
        res = 0
        for i in nums:
            res ^= i
        return res