l[LeetCode]#268. Missing Number

Environment : Python 3.7

Key technique: None

Example 1:

Input: [3,0,1]
Output: 2

Example 2:

Input: [9,6,4,2,3,5,7,0,1]
Output: 8

Analysis:

Use formula [(1+Input list size)*size]/2 to calculate sum. sum-Input sum =Output

Solution:

class Solution:
    def missingNumber(self, nums):
        sum_n=sum(nums)
        size=len(nums)
        total=int(((1+size)*size)/2)
        ans=total-sum_n
        return ans

Submitted result: