Number 268

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

from typing import List

class Solution:
    def missingNumber(self, nums: List[int]) -> int:
        sum_ = sum(nums)
        l_nums = len(nums)
        needed_sum = (l_nums*(l_nums+1))/2
        return int(needed_sum - sum_)

a = Solution()

print(a.missingNumber([3,0,1]))
print(a.missingNumber([0,1]))
print(a.missingNumber([9,6,4,2,3,5,7,0,1]))

2
2
8