Python3 appear only once digital

Original title https://leetcode-cn.com/problems/single-number/

topic:

Given a non-empty array of integers, in addition to an element appears only once, the rest of each element appears twice. To find out that only appears once in the elements.

Description:

Your algorithm should have linear time complexity. You can not use the extra space to achieve it?

Example 1:

输入: [2,2,1]
输出: 1

Example 2:

输入: [4,1,2,1,2]
输出: 4

Problem solving:

class Solution:
    def singleNumber(self, nums: List[int]) -> int:
        for i in range(1, len(nums)):
            nums[i] ^= nums[i-1]    #使用异或运算即可，且不需要额外空间，不用reduce是因为那会使用额外的存储空间
        return nums[-1]