Fifteen

In this exercise we will develop a model class for the Fifteen Puzzle:

The class must be called FifteenModel. Once it is complete you can extract the code in fifteen.zip to a folder on your computer. Put your model class in the same folder and then compile and run GraphicsMain.java. You will get a fully functional puzzle. Alternatively you can compile and run TextMain to get the same puzzle working in the terminal.

You need to complete four tasks:

1. The easiest way to model the state of the puzzle is via a two dimensional array of size 4 by 4. Each element in the array will contain a number from 0 to 15. When the number at position (i,j) is zero then this would mean that the hole in the puzzle is in position (i,j). If the number is between 1 and 15 then this means that the piece labeled with that number is at the corresponding position in the puzzle. In addition it would be handy to always keep track of the current position of the hole in separate integer variables.

   Define the following instance variables to model the state of the puzzle:

   private int[][] state;
   private int hrow, hcol;
   

   Here state is the array of numbers and hrow and hcol are the row and column where the hole is currently located.

   Define a constructor which initializes the variables in such a way that the initial state of the puzzle will be the same as on the picture above.

   public FifteenModel ()
   

2. Define a method getState which returns the current state at position (row, col).

   public int getState(int row, int col)
   

3. Define a method tryMovePieceAt which tries to move the hole to position (row, col). This is possible only if the hole is currently adjacent to the target position, i.e. it is located to the left, to the right, above or bellow the target position. If the hole is successfully moved then the method should return true, otherwise it must return false.

   public boolean tryMovePieceAt(int row, int col)
   

4. Define a method which shuffles the current state of the puzzle. The easiest way to do that is to call tryMovePieceAt one thousand times with a random row and column. Many of the movements will fail but enough will succeed to produce a shuffled puzzle.

   public void shuffle()