My answer to the missing number problem on Leetcode

missing_number.py

# https://leetcode.com/problems/missing-number/
import random


def generate_input_array(n: int) -> list:
    if not (1 <= n <= 104):
        raise ValueError('Given `n` does not fulfill 1 <= n <= 104')
    nums = list()
    while len(nums) != n:
        temp = random.randint(0, n)
        if temp not in nums:
            nums.append(temp)
    return nums


def find_missing_number_naive(nums: list, n: int) -> int:
    for i in range(n + 1):
        if i not in nums:
            return i
    return -1


def find_missing_number_xor(nums: list, n: int) -> int:
    missing = 0
    # XOR all values in range(0, n)
    for i in range(0, n + 1):
        missing ^= i

    # XOR all values in the `nums` array
    for i in nums:
        missing ^= i

    return missing


if __name__ == '__main__':
    n = 10
    nums = generate_input_array(n)
    assert len(nums) == n, "Expected length should be `n`"
    print(sorted(nums))
    naive = find_missing_number_naive(nums, n)
    assert naive != None, "Problem: given `nums` has no missing element."
    print(f'Naive solution gives us: {naive}')
    xor = find_missing_number_xor(nums, n)
    print(f'The O(1) solution using XOR gives us: {xor}')
    nums.append(xor)