Single Number

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?

URL: https://leetcode.com/problems/single-number/

class Solution(object):
    def singleNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if len(nums) == 0:
            return None
        elif len(nums) == 1:
            return nums[0]
        else:
            xor_prod = 0
            for entries in nums:
                xor_prod ^= entries 

            return xor_prod