Given an array containingndistinct numbers taken from0, 1, 2, ..., n, find the one that is missing from the array.

For example,
Givennums=[0, 1, 3]return2.

Note:
Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity?

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

class Solution(object):
    def missingNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if not nums:
            return None
        else:
            xor_prod = 0
            xor_prod_index = 0

            for i in range(len(nums)+1):
                xor_prod_index ^= i

            for i in range(len(nums)):
                xor_prod ^= nums[i]

            return xor_prod ^ xor_prod_index