Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.
Input: [3, 0, 1]
Output: 2
Input: [9,6,4,2,3,5,7,0,1]
Output: 8
Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.
Input: [3, 0, 1]
Output: 2
Input: [9,6,4,2,3,5,7,0,1]
Output: 8