Question

I want to create a Java method, which accepts an inputArray = Object[n][], where n can be any integer, and outputs a list of possible n-size combinations between all values of the n subarrays. Below is an example:

Input Array: (where Object=String and n=3)

String[] subarrayA = {"A0","A1","A2"};
String[] subarrayB = {"B0","B1"};
String[] subarrayC = {"C0","C1","C2","C3"};
String[3][] inputArray = {subarrayA, subarrayB, subarrayC};

Desired Output:

{A0,B0,C0},{A0,B0,C1},{A0,B0,C2},{A0,B0,C3},
{A0,B1,C0},{A0,B1,C1},{A0,B1,C2},{A0,B1,C3},
{A1,B0,C0},{A1,B0,C1},{A0,B0,C2},{A1,B0,C3},
{A1,B1,C0},{A1,B1,C1},{A1,B1,C2},{A1,B1,C3},
{A2,B0,C0},{A2,B0,C1},{A2,B0,C2},{A2,B0,C3},
{A2,B1,C0},{A2,B1,C1},{A2,B1,C2},{A2,B1,C3}

Obviously, I cannot have a fixed nested-loop inside my method since I do not know n in advance. So, I am guessing the only way to solve it would be through a recursive method? Any recommendations?

P.S: I am aware of the simple combination-related posts on the website.

Answer 1

This should solve your problem.

public static void permute(String array[][], int index, ArrayList<String> output){

    if(index == array.length){
        System.out.println(output.toString());
    }
    else{
        for(int i=0 ; i<array[index].length ; i++){
            output.add(array[index][i]);
            permute(array,index+1,output);
            output.remove(output.size() - 1); 
        }
    }
}