CSc 120: Battleship

Background

Restrictions

1. For the long problem, your code should follow the style guidelines for the class. You must follow the updated guidelines for commenting classes.
2. You may not use concepts and/or short-hand syntax not yet covered in class. The restrictions include the following:
   • dictionary or list comprehensions, e.g., [n * 2 for i in range(10)]
   • with open (explicitly open and close the file instead)
   • the ternary operator (use an if instead)
   • nested functions (using def within a function to define another function)
   • exceptions (try/except)
   • type annotations
   • lambda expressions
   • generators and user defined iterators
   • default arguments
   • decorators
   • importing libraries (unless a library is explicitly mentioned in the specification)

Problem Description

This program involves writing a program to model half of the actual board game, namely, Player 1's ship placements and Player 2's guesses.

The game setup. For the purposes of this program, the game board is a 10x10 grid. We use (x,y) coordinates to refer to the points of this grid: on each axis, grid values range from 0 through 9; the bottom-left corner has coordinates (0,0); and the top-right corner has coordinates (9,9).

Each player has five ships (one of each kind):

Ship type	Abbreviation	Size
Aircraft carrier	A	5
Battleship	B	4
Submarine	S	3
Destroyer	D	3
Patrol boat	P	2

Expected Behavior

Write a Python program, in a file battleship.py, that behaves as specified below.

1. Use input(), without any arguments, to read in the name of a placement file describing Player 1's ship placements. Read in the contents of the placement file and initialize the board accordingly.

   The format of the placement file is described below under Input Formats. The rules for legal placement are given in the link battleship-rules. An example placement file is shown in the file example-placement.txt.

2. Use input(), without any arguments, to read in the name of a guess file describing Player 2's guesses. Read in the contents and for each guess, respond based on the effects of the guess as described below.

   The format of a guess file is described below under Input Formats. The rules for legal guesses are given in the link battleship-rules. An example guess file is shown in the file example-guess.txt.

   Process the guess file as follows. For each guess:

   • If the guess is not legal: give the error message "illegal guess", discard the guess, and continue processing.

   • If the guess (x, y) is legal:
     1. If the grid point (x, y) is not occupied by any of Player 1's ships, indicate this as follows. If this is the first time this grid point has been guessed, print out the message "miss"; if this grid point has been guessed previously, print out the message "miss (again)".

     2. If (x, y) is occupied by some ship S, and at least one of the grid points occupied by S has not been hit by any of Player 2's guesses up to and including the current guess, indicate this using as follows. If this is the first time this grid point has been guessed, print out the message "hit"; if this grid point has been guessed previously, print out the message "hit (again)".

     3. If (x, y) is occupied by some ship S, and all of the grid points occupied by S have been hit by Player 2's guesses up to and including the current guess (i.e., this guess hits the last grid point of S that was not previously hit), indicate this using the statement

        print("{} sunk".format(ship))

        where ship is one of { 'A', 'B', 'S', 'D', 'P' } and refers to the ship occupying the grid point (x, y).
     4. If, after this guess, all of Player 1's ships have been sunk, indicate this using the following statement and then exit the program:

        print("all ships sunk: game over").

3. The game ends (the program terminates) when either all of the ships have been sunk, or there are no more guesses to respond to.

An example of the program's expected behavior is given Battleship Input/Output Example. The input files corresponding to this example are available as example-placement.txt (placement file) and example-guess.txt (guess file). The rules for legal guesses are given in the link battleship-rules.

Input Formats

I. Player 1's ship placements

This is done by specifying the placement of each ship in turn. Each ship's placement has the following form:

Abbreviation x₁ y₁ x₂ y₂

For example:

B   3   2   3   5

II. Player 2's guesses

Each guess is a pair of integers on a single line specifying a grid point. The rules for legal guesses are given in the link battleship-rules.

Programming Requirements

class GridPos

An instance of this class describes a grid position.

Attributes: These should include:

• the x- and y-coordinates of the position;
• the Ship object at that position, if any, and None if the position is unoccupied; and
• whether or not it has been previously guessed.

Methods: These should include __init__() and __str__() methods; and, optionally, a __repr__() method.

class Board

An instance of this class describes a board with a placement of ships.

Attributes: These should include:

• a 10 × 10 grid of positions, where each position is a GridPos object; and
• a collection (e.g., list, set, or dictionary) of Ship objects.

Methods: These should include:

• a method to process guesses.
• __init__() and __str__() methods.

class Ship

An instance of this class represents a ship.

Attributes: These should include:

• the kind of ship (see the table at the top of this page);
• the size of the ship;
• the grid positions occupied by the ship; and
• the number of grid positions occupied by the ship that have not yet been hit.

Methods: __init__() and __str__() methods.

Errors

Use if statements to detect these errors (that is, don't use asserts or try/except) and perform the actions specified below.

1. There should be 5 ships, one of each type; if not print the following error message and quit:

   Error message: "ERROR: fleet composition incorrect"

2. If the ship is out of the grid area, print the following error message and quit:

   Error message: "ERROR: ship out-of-bounds: " + line

3. If the ship is not horizontal or vertical, print the following error message and quit:

   Error message: "ERROR: ship not horizontal or vertical: " + line

4. If the ship overlaps with another ship, print the following error message and quit:

   Error message: "ERROR: overlapping ship: " + line

5. If the ship is an incorrect size for its type, print the following error message and quit:

   Error message: "ERROR: incorrect ship size: " + line

6. If a guess is at a position not within the board, print the following error message, discard the guess, and continue processing:

   Error message: "illegal guess"

Note: You must handle the errors in the order listed above so that your output matches the output expected by the autograder.

To help simplify the logic of your code to terminate the program after the errors in items 1-5 above are reported, you may use Python's system library. First, include the following import statement at the top of your program:

import sys

sys.exit(0)

Examples

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