【LeetCode】268. 缺失数字

给定一个包含 0, 1, 2, ..., n 中 n 个数的序列，找出 0 .. n 中没有出现在序列中的那个数。

示例 1:

输入: [3,0,1]
输出: 2

示例 2:

输入: [9,6,4,2,3,5,7,0,1]
输出: 8

#!/usr/bin/python3
# -*- coding: utf-8 -*-
# @Time: 2018/8/16
# @Author: xfLi
# 缺失数 = 前n项和 - nums

def missingNumber(nums):
    """
    :type nums: List[int]
    :rtype: int
    """
    n = len(nums) + 1
    sum_nums = n * (n - 1) / 2
    part_nums = sum(nums)
    return int(sum_nums - part_nums)

if __name__ == '__main__':
    nums = [9,6,4,2,3,5,7,0,1]
    result = missingNumber(nums)
    print(result)