// This program prompts shows a user all of the ways to make change for
// a specific amount.

import java.util.*;

public class Change {
    public static void main(String[] args) {
        System.out.println(" P  N  D  Q");
        System.out.println("------------");
        showChange(28);
    }

    // Shows all ways to make change for the given amount
    public static void showChange(int amount) {
        List<Integer> coinValues = new LinkedList<Integer>();
        coinValues.add(1);
        coinValues.add(5);
        coinValues.add(10);
        coinValues.add(25);
        
        // ... your code goes here ...
        Stack<Integer> chosen = new Stack<Integer>();
        explore(amount, coinValues, chosen);
    }

    // Shows all ways to make change for the given amount and coin values,
    // given the stack of existing number of coins already chosen.
    private static void explore(int amount, List<Integer> coinValues,
                                Stack<Integer> chosen) {
        if (coinValues.isEmpty()) {
            // base case: no coins left to choose.
            if (amount == 0) {
                System.out.println(chosen);
            }
        } else {
            // recursive case: grab coin value (penny, nickel, etc.) from list
            int coinValue = coinValues.remove(0);
            for (int i = 0; i <= (amount / coinValue); i++) {
                // try each value i from 0 to the max # possible of this coin
                chosen.push(i);
                
                // explore the other coin values recursively
                explore(amount - (i * coinValue), coinValues, chosen);
                
                chosen.pop();               // unmake the choice (1st half)
            }
            
            coinValues.add(0, coinValue);   // unmake the choice (2nd half)
        } 
    }
}