268. Missing Number

public class Solution {
    public int missingNumber(int[] nums) {
        int SIZE = nums.length;
        int sumExpected = SIZE*(SIZE+1)/2; 
        int sumActual = 0;
        for(int i = 0; i < SIZE; i++){
            sumActual += nums[i];
        }
        return sumExpected-sumActual;
    }
}