public class main{
    public static int arraySum(int[] arr){
        int sum = 0;
        for (int i : arr){
            sum += i;
        }
        return sum;
    }

    public static int[] rowSums(int[][] Arr2D){
        int[] sums = new int[Arr2D.length];
        for (int i = 0; i < Arr2D.length; i ++){
            sums[i] = arraySum(Arr2D[i]);
        }
        return sums;
    }

    public static boolean isDiverse(int[][] Arr2D){
        int[] sums = rowSums(Arr2D);
        for (int i = 0; i < sums.length; i ++){
            for (int j = i + 1; j < sums.length; j ++){
                if (sums[i] == sums[j]){
                    return false;
                }
            }
        }
        return true;
    }

    public static void main(String args[]){
        int[] arr = new int[]{1, 3, 2, 7, 3};
        System.out.println(arraySum(arr));

        int[][] Arr2D = {
            {1, 3, 2, 7, 3},
            {10, 10, 4, 6, 2},
            {5, 3, 5, 9, 6},
            {7, 10, 8, 2, 1}
        };
        for (int i : rowSums(Arr2D)){
            System.out.println(i);
        }
        System.out.println(rowSums(Arr2D));

        System.out.println(isDiverse(Arr2D));
    }
}  

main.main(null)

16
16
32
28
28
[I@580f75c1
false

Learnings:

  1. How to properly define an array. Originally I wrote it as: int[] arr = [1, 3, 2, 7, 3]; but it should actually be int[] arr = new int[]{1, 3, 2, 7, 3};
  2. How to properly define a 2d Array
  3. When initializing an Array I have to put int the length of it
  4. In order to find the length of array I use .length as a property not a method.
  5. No .append(), have to just set the value which works because the length of the array is already set.

Reflection:

This FRQ had me working with 2d arrays. This was interesting to me, since I hadn’t had a lot of experience directly defining 2d arrays in Java before. I do feel very comfortable with this topic though and most of the trouble I had was with the syntax rather than anything conceptual.