Harvey Mudd College

Computer Science 60

Spring 1998

Assignments 5 and 6

Assignment 5 due Thurs. 3/5/98, 50 points

Assignment 6 due Thurs. 3/12/98, 50 points

Maze Maker

Assignment 5 will provide an opportunity to create an applet with simple graphics. Assignment 6 extends this to use a queue (similar to one you constructed in assignment 4) to perform breadth-first search of a maze. Maze Maker is a tool for constructing mazes. The user drags the mouse within the rectangular field to create internal walls, as shown in blue above. The object of the maze player is to find a path constructed by the user. Maze Maker is required to display a minimal-length path through the maze, as shown in red above. In Assignment 5, your applet need only allow the user to draw a maze. In assignment 6, path creation is tobe added.

The rules for maze creation (assignment 5) are as follows:

• The drawing field is a grid made of squares of 10 pixels on a side, 30 by 50 squares total, including outer walls.
• When the user depresses the mouse button, if the cursor is over a blank square (or a previously-drawn path square), draw mode is indicated. If the cursor is over a wall square when the mouse is depressed, erase mode is indicated.
• In draw mode, a background square over which the mouse button was depressed, and any squares over which the mouse is dragged, are changed into wall squares if they are not wall squares already.
• In erase mode, the wall square over which the mouse is depressed, and any squares over which the mouse is dragged, are erased.
• The start and finish squares of the maze are fixed to the upper left and lower right areas of the maze, as shown in the drawing. These squares and the outer wall squares are never modified by the user.
• Add a Clear button which removes everything which has been drawn.
• On the sample, you will notice a logo when the applet first opens; this is not required.

The rules for path creation (assignment 6) are as follows:

• The path, if any, is drawn in red, when the mouse button is released.
• While the user is drawing, the previous path remains on the screen, except as overwritten by drawing.
• The path must be minimal-length, in the sense that there is no shorter path from start to finish.
• A path moves only vertically or horizontally from square to square, not diagonally.
• If there is no path possible, then no red squares are drawn.

You may want to check out Square.java (run the applet) to see how to draw a square and track mouse events. Use the method of an off-screen buffer, as discussed in class and shown in the example, so that your applet does not flicker. This is mandatory. Applets require an html file. The text for this one is Square.html.

For the path-finding, breadth-first search will be explained in the lecture.You may also read about breadth-first search of a graph in the low-level functional programming chapter. The concept is the same, but the graph is implicit in the case of a maze.