Lab 8: Column Puzzle

Download and unzip lab8.zip, which contains all the files you will need for this assignment. Open the file Puzzle.java in DrJava. All the code you write for this assignment should be added to this file.

Be sure to test your code after completing each exercise.

The Puzzle

In this lab, you'll be implementing a "column puzzle," like the one shown here:

This toy consists of 6 columns of colored plastic tiles--3 per column, with one space left empty. A tile can be moved vertically into the empty space. The toy also consists of 3 horizontal wheels, each of which can be turned to the left or right. The object of the game is to line up the tiles so that each column consists of exactly one color. We will represent this game on the computer screen as shown here:

Eventually, clicking on an arrow will turn the wheel for that row, sliding all the tiles on that row in the direction of the arrow. Clicking on a tile that is just above or below the empty location (shown in black) will slide that tile into the empty location.

The puzzle is implemented using the Grid file. The grid has 3 rows and 8 columns. The arrows appear in columns x=0 and x=7. The tiles appear in columns x=1 through x=6.

drawArrows

Compile and run Puzzle.java. This will run the main method. You should see an empty black window appear. The main method calls the setup method, which creates the window and calls drawArrows and drawTiles. Complete the drawArrows method, so that it places the "left.gif" and "right.gif" arrow images in the appropriate locations of the grid. Test that you see these arrows appear correctly when you run your program.

isEmpty

Complete the isEmpty method, which should only return true if the color at (x, y) is black.

drawOneTile

Complete the drawOneTile method, which should draw one tile in the given color. The tile should be placed in a random empty location. Here's how:

  1. Assign random integers to variables x and y, corresponding to one of the 18 possible locations where a tile can appear in the grid.
  2. Repeat until the location at (x, y) is empty:
  3. Set the color at (x, y) to be the color given in the method's parameters.

Test your code by running your program, and then calling drawOneTile in the Interactions pane. Call it multiple times, and make sure a new tile appears each time, and that no existing tiles change.

drawAllTiles

The drawAllTiles method is called by setup. Complete the drawAllTiles method, which should use drawOneTile to draw 3 blue tiles, 3 red tiles, 3 green tiles, 3 yellow tiles, 3 magenta tiles, and 2 cyan tiles. Run your program and make sure you see these 17 tiles appear.

swapTiles

Complete the swapTiles method, which should swap the tile at (x1, y1) with the tile at (x2, y2).

Test your code by running your program, and then calling swapTiles in the Interactions pane.

slideOneTile

Complete the slideOneTile method, which should attempt to slide the tile at the given (x, y) location up or down one row, into an empty location. If the tile is not above or below an empty location, then this method should do nothing.

If the location immediately above (x, y) is empty, then slide the tile up. (Of course, if (x, y) is in the top row, then there won't be a location above it.) If, instead, the location immediately below (x, y) is empty, then slide the tile down. Call the swapTiles method to slide the tile. Test your code by running your program, and then calling slideOneTile in the Interactions pane. Be sure to test a variety of cases.

slideLeft

Complete the slideLeft method, which should slide all the tiles in row y to the left, by one column. The leftmost tile should wrap around to become the rightmost tile. Here's how:

  1. Save the color of the leftmost tile in row y in appropriate variables.
  2. Swap the tile in column x=1 with the tile in column x=2.
  3. Swap the tile in column x=2 with the tile in column x=3.
  4. Swap the tile in column x=3 with the tile in column x=4.
  5. Swap the tile in column x=4 with the tile in column x=5.
  6. Swap the tile in column x=5 with the tile in column x=6.
  7. Set the color of the rightmost column in row y to be the color you saved earlier.
Test your code by running your program, and then calling slideLeft in the Interactions pane.

slideRight

Complete the slideRight method, which should slide all the tiles in row y to the right, by one column. The rightmost tile should wrap around to become the leftmost tile. The code should be very similar to slideLeft, with a few key differences. Which tile's colors should you save at the beginning of your method? Which two tiles should you swap first? Which two tiles should you swap next? Which location should you set the color of, at the end of your method?

Be sure to test your code.

play

Modify the main method so that, after setting up the puzzle, it calls the play method, which should let the user attempt to solve the puzzle.

The play method repeatedly waits for the user to click on a location of the grid, and stores the coordinates of that location in (x, y). Insert code inside the loop. If the user clicked on an arrow, call slideLeft or slideRight to slide the appropriate row in the given direction. If the user clicked on a tile, call slideOneTile.

Now run your program and try to solve your puzzle.

Challenges