LeetCode268 Missing Number

描述

Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.

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

样例

Given nums = [0, 1, 3] return 2.

思路

$0$$n$ 之和 再扣掉 数组元素之和，即得到答案。