• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
timothyjlaird

asking for tic-tac-toe AI help

2 posts in this topic

I've been writing a simple tic-tac-toe game to get a grounding in Python and AI (minimax algorithm). I've got something working but I'm stuck on the AI part.

 

I *think* that I understand the theory of minimax in this case...given the current game state...you run through every possible outcome...if you hit a leaf that results in a win you add +1 to the root node that represents the next player choice...if the leaf results in a loss you subtract 1...then you play out the root node with the highest value? Is that correct?

 

I know this probably requires recursion but that has never been something I've been good at.

 

My code is pretty simple...I keep an unordered set of human moves made and a set of ai moves made. When a move is made by either the human or ai, it gets added to the appropriate set. I check each set at the end of the turn for a win or a tie. I've gotten it to the point where it randomly plays against itself (given a human set and an ai set with the list of moves already made) but I'm not quite sure where to go from there.

 

I hate doing this but I've been on this for hours...can someone give me a shove in the right direction? The code listing is below. Calling 'playcycle()' runs the game with prompts for human input and randomly chose 'computer' moves. Calling 'playoutaiall()' plays 10 random games and prints out the result for each.

import random

#checks a player set (either human or ai) for a possible win
def checkforwin(moves):
    if '1' in moves:
        if '2' in moves and '3' in moves:
            return True
        if '4' in moves and '7' in moves:
            return True
        if '5' in moves and '9' in moves:
            return True
    if '9' in moves:
        if '7' in moves and '8' in moves:
            return True
        if '3' in moves and '6' in moves:
            return True
    if '4' in moves and '5' in moves and '6' in moves:
        return True
    if '2' in moves and '5' in moves and '8' in moves:
        return True
    if '7' in moves and '5' in moves and '3' in moves:
        return True
    return False

#given human and ai move sets, returns remaining valid moves
def getmovesleft(playermoves, aimoves):
    allmoves = set('123456789')
    return allmoves - (playermoves | aimoves)

#given human and ai move sets, prints board state
def printboard(playermoves, aimoves):
    count = 1
    while (count < 10):
        if str(count) in playermoves:
            print('x', end="")
        elif str(count) in aimoves:
            print('o', end="")
        else:
            print(str(count), end="")
        if count % 3 == 0:
            print('\n', end="")
        count = count + 1

#returns whether a particular move is valid, given human and ai moves sets
def isvalidmove(newmove, playermoves, aimoves):
    return newmove in getmovesleft(playermoves, aimoves)

#given a set of remaining valid moves, returns one at a random
def generateaimove(aimovesleft):
    return random.sample(aimovesleft, 1)

#given human and player move sets, gets a valid move from the human player and returns it
def makehumanplayermove(playermoves, aimoves):
    print('It is your move! Current board state...')
    printboard(playermoves, aimoves)
    movesleft = getmovesleft(playermoves, aimoves)
    while True:
        print('Possible moves' , movesleft)
        move = input('Enter a move: ')
        if isvalidmove(move, playermoves, aimoves) == True:
            return move

#given sets of human and ai moves already made, returns a valid move
def makeaiplayermove(playermoves, aimoves):
    move = generateaimove(getmovesleft(playermoves, aimoves))
    return move

#given a player move and sets of existing (already played) human and ai moves, play out one turn (or cycle)
def singlecycle(pmove, playermoves, aimoves):
    playermoves.update(pmove)
    if checkforwin(playermoves) == True:
        return 'pwin'
    if len(getmovesleft(playermoves, aimoves)) == 0:
        return 'tie'
    aimove = makeaiplayermove(playermoves, aimoves)
    aimoves.update(aimove)
    if checkforwin(aimoves) == True:
        return 'aiwin'
    if len(getmovesleft(playermoves, aimoves)) == 0:
        return 'tie'
    return 'continue'

#given an end of game result, print it out for the human's benefit
def printgameresult(endresult):
    if endresult == 'pwin':
        print('The human won!')
    elif endresult == 'aiwin':
        print('The AI won. No suprise there. Stupid human...')
    elif endresult == 'tie':
        print('A tie game? How boring!')

#given a list of existing player and ai move sets, play out a complete game at random (no human input)
def playoutai(playermoves, aimoves):
    while True:
        randomplayermove = makeaiplayermove(playermoves, aimoves)
        cycleresult = singlecycle(randomplayermove, playermoves, aimoves)
        if cycleresult != 'continue':
            printboard(playermoves, aimoves)
            print('ai moves:' , aimoves)
            print('player moves:', playermoves)
            printgameresult(cycleresult)
            break

#play out 10 complete games
def playoutaiall():
    count = 0
    while count < 10:
        player = set()
        ai = set()
        playoutai(player, ai)
        count = count + 1

#play out a complete game with human input
def playcycle():
    playermoves = set()
    aimoves = set()
    print('Welcome to a new game!')
    
    while True:
        move = makehumanplayermove(playermoves, aimoves)
        cycleresult = singlecycle(move, playermoves, aimoves)
        if cycleresult != 'continue':
            printgameresult(cycleresult)
            break
        
    #end of current game
    print('End board state...')
    printboard(playermoves, aimoves)

I think all my base logic is there for AI but I'm not sure where to go from here. Any help would be much appreciated.

 

Thanks,

John

Edited by timothyjlaird
0

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0