NoOfStories.java

/**
 * Created by rg3 on 10/17/17.
 */

import java.util.ArrayList;

public class NoOfStories {
    static int small=1;
    static int large=2;

    public static  ArrayList<ArrayList<String>> combinations(int stories) {
        ArrayList<ArrayList<String>> result = new ArrayList<>();

        //start from an empty list
        result.add(new ArrayList<>());

        for (int i = 0; i < stories; i++) {
            //list of list in current iteration of the array stories
            ArrayList<ArrayList<String>> current = new ArrayList<>();

            for (ArrayList<String> l : result) {
                // # of locations to insert is largest index + 1
                for (int j = 0; j < l.size()+1; j++) {
                    // + add stories[i] to different locations
                    if (j/large ==0) {
                        l.add(j, "small");

                    } else {
                        l.add(j, "large");

                    }
                    //l.add(j, i);

                    ArrayList<String> temp = new ArrayList<>(l);
                    current.add(temp);

                    //System.out.println(temp);

                    // - remove stories[i] add
                    l.remove(j);
                }
            }

            result = new ArrayList<ArrayList<String>>(current);
        }

        return result;    }

    public static void main(String[] args) {
        System.out.println(combinations(3));
    }
}