Given an array containingndistinct numbers taken from0, 1, 2, ..., n, find the one that is missing from the array.

Example 1

Input:
 [3,0,1]

Output:
 2

Example 2

Input:
 [9,6,4,2,3,5,7,0,1]

Output:
 8

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

Credits:
Special thanks to@jianchao.li.fighterfor adding this problem and creating all test cases.

class Solution {
    public int missingNumber(int[] nums) {
        int sum = 0;
        for (int num : nums){
            sum += num;
        }

        int supposed = (nums.length + 1) * nums.length / 2;

        return supposed - sum;
    }
}