LeetCode - 268. Missing Number

Q：

Given an array containing n distinct numbers taken from

0, 1, 2, ..., n

, find the one that is missing from the array.

For example,

Given nums =

[0, 1, 3]

return

2

.

Note:

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

Credits:

Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

A：

class Solution(object):
def missingNumber(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
numsCount = len(nums)
return numsCount * (numsCount + 1) / 2 - sum(nums)