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