Creating a new 2D array that = size of 2D array 1 + size of 2d array 2 (rows and columns)

Question

public static int[][] add2DArrays(int[][]A, int[][]B) {
        return int[][] C;
}

I understand how to populate this new array by adding the sums of the two arrays A & B, the road block I am facing is creating this initial array C. We cannot assume the size of the arrays given as parameters, so that is the part I am having a problem with.

I know by doing:

 int[][] C = new int[A.length+B.length][]; //this will only give me the # of rows;

I am stuck on how to get the proper length of columns for the rows in the new array. I am thinking it may be possible to some how record the length of the longest row in A, and then record the longest row in B, and choose the bigger of the two, but that seems messy and inefficient. Thank you all for your support.

Answer 1

If both are really 2D arrays -- that is, the length of all the rows is the same -- and row 0 was actually allocated, you can get the summed length of a row from A[0].length+B[0].length

If the length of the rows might vary -- which is perfectly legal in Java -- then you might need to iterate through A and B to find the longest row and use that length.