Problem
Given an array containing n distinct numbers drawn from the range [0, n], exactly one number in that range is missing. Find it.
Input / Output
- Input: int array nums of length n (distinct, all in [0, n]).
- Output: the missing number.
Constraints
- 0 ≤ n ≤ 10^4; aim for O(n) time and O(1) extra space.
Example
- [3,0,1] → 2; [0,1] → 2; [9,6,4,2,3,5,7,0,1] → 8.