Question

currently recursion is fresh & difficult topic for me, however I need to use it in one of my algorithms.

Here is the challenge:

I need a method where I specify number of recursions (number of nested FOR loops) and number of iterations for each FOR loop. The result should show me, something simmilar to counter, however each column of counter is limited to specific number.

ArrayList<Integer> specs= new ArrayList<Integer>();
  specs.add(5); //for(int i=0 to 5; i++)
  specs.add(7);
  specs.add(9);
  specs.add(2);
  specs.add(8);
  specs.add(9); 

public void recursion(ArrayList<Integer> specs){
  //number of nested loops will be equal to: specs.size();
  //each item in specs, specifies the For loop max count e.g:
  //First outside loop will be: for(int i=0; i< specs.get(0); i++)
  //Second loop inside will be: for(int i=0; i< specs.get(1); i++)
  //...
}

The the results will be similar to outputs of this manual, nested loop:

    int[] i;
    i = new int[7];

    for( i[6]=0; i[6]<5; i[6]++){
        for( i[5]=0; i[5]<7; i[5]++){
            for(i[4] =0; i[4]<9; i[4]++){
                for(i[3] =0; i[3]<2; i[3]++){
                    for(i[2] =0; i[2]<8; i[2]++){
                        for(i[1] =0; i[1]<9; i[1]++){
                            //...
                            System.out.println(i[1]+" "+i[2]+" "+i[3]+" "+i[4]+" "+i[5]+" "+i[6]);
                        }
                    }
                }
            }
        }
    }

I already, killed 3 days on this, and still no results, was searching it in internet, however the examples are too different. Therefore, posting the programming question in internet first time in my life. Thank you in advance, you are free to change the code efficiency, I just need the same results.

Answer 1

Does this snippet give the output you want? (It is compileable and executeable)

import java.util.ArrayList;
import java.util.List;

public class SO {

    static ArrayList<Integer> specs = new ArrayList<Integer>();
    static int[] i;

    public static void main(String[] args) throws Exception {
        specs.add(5); //for(int i=0 to 5; i++)
        specs.add(7);
        specs.add(9);
        specs.add(2);
        specs.add(8);
        specs.add(9);
        i = new int[specs.size()];
        printMe(0, specs, i);
    }

    static void printMe(int depth, List<Integer> _specs, int[] i) {
        if (_specs.isEmpty()) {
            System.out.println(printI(i));
            return;
        } else {
            for (int j = 0; j < _specs.get(0); j++) {
                i[depth] = j + 1; // + 1 since you seems to want to go from 1 and not 0
                printMe(depth + 1, _specs.subList(1, _specs.size()), i);
            }
        }
    }

    static String printI(int[] i) {
        StringBuilder sb = new StringBuilder();
        for (int j = 0; j < i.length; j++) {
            sb.append(i[j]);
            if (j < i.length - 1) {
                sb.append(" ");
            }

        }
        return sb.toString();
    }
}