On 02/02/06, Alan Gauld <[EMAIL PROTECTED]> wrote:
Yes if you let it!
No, if you look at the code below, it has a predefined set of 'best moves'.
Thanks to André, there is a way to win every time if you take the first move (see below), so there MUST be a whole in the computers stratergy! Based on what we all know about the game, I would say that you can not make it so that the computer can win every time, but it should be possable to make it tie.
x: 0
o: 4
x: 7
o: 2
x: 6
Bob,
>> Write a new computer_move() function for the tic-tac-toe game to plug
>> the hole in the computers stratergy. See if you can create an opponent
>> that is unbeatable!
>>
>> My main problem is that I can not see how the computers stratergy can
>> be improved as at best I can only manage a tie with the computer!
Does the computer ever go first?
Yes if you let it!
Does the computer start with a random location?
No, if you look at the code below, it has a predefined set of 'best moves'.
If yes to the above then the computer can be beaten since the entire
course of a Tic-Tac-Toe game (or OXO as we call it in the UK!)
depends upon the first move location.
Thanks to André, there is a way to win every time if you take the first move (see below), so there MUST be a whole in the computers stratergy! Based on what we all know about the game, I would say that you can not make it so that the computer can win every time, but it should be possable to make it tie.
x: 0
o: 4
x: 7
o: 2
x: 6
If no to the above then, provided the gameplay is OK, I don't know
what the author means either.
Alan G.
The code is as follows:
# set global constants
X = "X"
O = "O"
EMPTY = " "
TIE = "TIE"
NUM_SQUARES = 9
# set game instructions
def display_instruct():
"""Display game instructions."""
print \
"""
Welcome to the greatest intellectual challenge of all time: Tic-Tac-Toe.
This will be a showdown between your human brain and my silicon processor.
You will make your move known by entering a number, 0 - 8. The number
will correspond to the board position as illustrated:
0 | 1 | 2
---------
3 | 4 | 5
---------
6 | 7 | 8
Prepare yourself, human. The ultimate battle is about to begin. \n
"""
# set question
def ask_yes_no(question):
"""Ask a yes or no question."""
response = None
while response not in ("y", "n"):
response = raw_input(question).lower()
return response
# set ask number
def ask_number(question, low, high):
"""Ask for a number within the range"""
response = None
while response not in range(low, high):
response = int(raw_input(question))
return response
# set pieces
def pieces():
"""Determine if player or computer goes first."""
go_first = ask_yes_no("Do you wish to go first? (y/n): ")
if go_first == "y":
print "\nThen take the first move. You will need it ;)"
human = X
computer = O
else:
print "\nYour bravery will be your undoing....I will go first."
computer = X
human = O
return computer, human
# create new board
def new_board():
"""Create a new game board."""
board = []
for square in range(NUM_SQUARES):
board.append(EMPTY)
return board
# display the board
def display_board(board):
"""Display the board on the screen"""
print "\n\t", board[0], "|", board[1], "|", board[2]
print "\t", "---------"
print "\t", board[3], "|", board[4], "|", board[5]
print "\t", "---------"
print "\t", board[6], "|", board[7], "|", board[8], "\n"
# set legal moves
def legal_moves(board):
"""Create list of legal moves."""
moves = []
for square in range(NUM_SQUARES):
if board[square] == EMPTY:
moves.append(square)
return moves
# set winner
def winner(board):
"""Determine the game winner"""
WAYS_TO_WIN = ((0, 1, 2),
(3, 4, 5),
(6, 7, 8),
(0, 3, 6),
(1, 4, 7),
(2, 5, 8),
(0, 4, 8),
(2, 4, 6))
for row in WAYS_TO_WIN:
if board[row[0]] == board[row[1]] == board[row[2]] != EMPTY:
winner = board[row[0]]
return winner
if EMPTY not in board:
return TIE
return None
# set human move
def human_move(board, human):
"""Get human move."""
legal = legal_moves(board)
move = None
while move not in legal:
move = ask_number("Where will you move? (0-8): ", 0, NUM_SQUARES)
if move not in legal:
print "\nThat square is already occupied. Please choose another.\n"
print "Fine..."
return move
# set computer move
def computer_move(board, computer, human):
"""Make computer move."""
# Make a copy of the board to work with since the function will be changing the list
board = board[:]
# The best positions to have, in order
BEST_MOVES = (4, 0, 2, 6, 8, 1, 3, 5, 7)
print "I shall take a square number",
# if computer can win, take that move
for move in legal_moves(board):
board[move] = computer
if winner(board) == computer:
print move
return move
# done checking this move, undo it
board[move] = EMPTY
#if human can win, block that move
for move in legal_moves(board):
board[move] = human
if winner(board) == human:
print move
return move
# done checking this move, undo it
board[move] = EMPTY
# since no one can win on next move, pick best open square
for move in BEST_MOVES:
if move in legal_moves(board):
print move
return move
# set next turn
def next_turn(turn):
"""Switch turns."""
if turn == X:
return O
else:
return X
# congratulate winner
def congrat_winner(the_winner, computer, human):
"""Congratulate the winner"""
if the_winner != TIE:
print the_winner, "won!\n"
else:
print "Its a tie!\n"
if the_winner == computer:
print "As I predicted human, I am triumphant once more. \n" \
"Proof that computers are superior to humans in all regards."
elif the_winner == human:
print "Nooooo! It cannot be! Somehow you tricked me human! \n" \
"But never again.......I will win next time!"
elif the_winner == TIE:
print "You were most lucky human, and somehow managed to tie me! \n" \
"Celebrate today....for this will not happen again!"
# set main function
def main():
display_instruct()
computer, human = pieces()
turn = X
board = new_board()
display_board(board)
while not winner(board):
if turn == human:
move = human_move(board, human)
board[move] = human
else:
move = computer_move(board, computer, human)
board[move] = computer
display_board(board)
turn = next_turn(turn)
the_winner = winner(board)
congrat_winner(the_winner, computer, human)
# start the program
main()
raw_input("\n\nPress the enter key to exit.")
--
Best Regards
Jon Moore
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