Missing Number

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

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

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

Solution:

public class Solution {
    public int missingNumber(int[] nums) {
        int sum = 0;
        for(int n : nums) sum += n;
        return nums.length*(nums.length+1)/2 - sum;
    }
}