Ggtcf

I'm working on a function which breaks down the given input into denominations using a recursive call.

At each step it recurses into two variants:

1. Continue with the current coin: Add it to the list and recurse.


2. Switch to the next coin: Increment coin pos and recurse.

In addition to printing out the combination of denominations captured in the list when remaining == 0, I intend to capture the value of that list and return it from the function.

Here's the code:

 static final int[] DENOMINATIONS = 9,5,3;

 private static void change(int remaining, List<Integer> coins, int pos)

 if (remaining == 0) 

 // This correctly prints the desired output. 
 // I want to return that exact value from the function.
 System.out.println(coins); 

 else 
 if (remaining >= DENOMINATIONS[pos]) 
 coins.add(DENOMINATIONS[pos]);
 another.addAll(coins);
 change(remaining - DENOMINATIONS[pos], coins, pos);
 coins.remove(coins.size() - 1);
 
 if (pos + 1 < DENOMINATIONS.length) 
 change(remaining, coins, pos + 1);
 
 
 }


 public static List<Integer> denominations(int amount) 
 List<Integer> result = new ArrayList<Integer>();
 List<Integer> another = new ArrayList<Integer>();
 change(amount, result, another ,0);
 System.out.println(another.size());
 return another;
 

 public static void main(String[] args) 
 List<Integer> list = denominations(13);
 System.out.println(list);
 

Output : [5, 5, 3]

You seems to assume that java is passed by reference which is not true. Java methods are passed by value.

I have updated your code:

change method:

private static List<Integer> change(int remaining, List<Integer> coins, int pos) // Updated method return type;

 if (pos < 0 

denominations method:

public static List<Integer> denominations(int amount) 
 return change(amount, new ArrayList<Integer>(), 0);

INPUT : 13
OUTPUT : [5, 5, 3]

You would have to add return coins; at the and of change method, but you can keep it the way you have it. Returning and changing an array is a code smell as the method both operates on object (modifies it) and returns a result.

To make it work, you can define your denomination method as follows:

public static List<Integer> denominations(int amount) 
 List<Integer> result = new ArrayList<Integer>();
 change(amount, result, 0);
 return result;

Edit:

The list is empty because the only place it's changed is here:

coins.add(DENOMINATIONS[pos]);
change(remaining - DENOMINATIONS[pos], coins, pos);
coins.remove(coins.size() - 1);

Where an element is added and removed. It's what you have written that makes it empty:)

Edit2:

I would suggest passing around a second object, that would be a copy of the list you would like to return and is not modified.

change should return boolean that mean whether has been found an answer.

So change body looks like this:

if (remaining == 0) 
 return true;

...
if (change(...)) return true;
...
return false; // It's last line of body