Golf this AP CS Java FRQ - Duplicate Sums of Arrays in 2D Array

Question

In preparation for the AP Computer Science AP Test (Java), our teacher has been giving us FRQs from previous years for practice.

My friend and I were golfing this during class today and got it as short as we could, but I'd like to see if there are any shorter solutions any of you can come up with.

Rules:

• You must use the predefined method headers, method names, and parameter names.
• You do not have to specify imports.
• All code is to be written in Java.
• No external libraries

Information:

Part A

Given an array of type int, write a method that returns the sum of the elements of the array.

public int arraySum(int[] arr)
{
    /*Implementation to be written in part A*/
}

Now, write the implementation for the method arraySum.

Part B

Given a 2D array of type int, write a method that returns a 1-dimensional int array containing the sums of each row of the given 2-dimensional array. You must use arraySum but may assume it works properly regardless of what you put for part A.

public int[] array2dSum(int[] arr2d)
{
    /*Implementation to be written in part B*/
}

Now, write the impmenetation for the method array2dSum.

Part C

Given a 2D array of type int, write a method that returns whether or not the sums of the rows of the array are diverse, meaning the array contains no duplicate sums. You must use array2dSum but may assume it works properly regardless of what you put for part A.

public boolean isDiverse(int[] arr2d)
{
    /*Implementation to be written in part C*/
}

Now, Write the implementation for the method isDiverse.

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Here's what I have:

A - 31 chars

return IntStream.of(arr).sum();

B - 59 chars

return Stream.of(arr2d).mapToInt(x->arraySum(x)).toArray();

C - 86 chars

int[]h=array2dSum(arr2d);return IntStream.of(h).distinct().toArray().length==h.length;

---

Test Inputs:

arraySum(new int[] {1, 2, 3}) returns 6

array2dSum(new int[][] {{1,2},{3,4}}) returns {3,7}

isDiverse(new int[][] {{1,2,3},{4,5,6},{7,8,9}}) returns true

isDiverse(new int[][] {{1,2,3},{4,5,6},{1,2,3},{7,8,9}}) returns false