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## Minimax Algorithm Help

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### #1AF1992  Members

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Posted 07 May 2014 - 01:55 PM

Hello, I've been working on basic A.I. algorithms in C++ over the last week and I've hit a wall. I've written a basic hard-coded logic FSM TicTacToe game and I then attempted to implimented a Minimax algorithm using the information provided in the following post:

http://www.gamedev.net/topic/562118-minimax-for-tic-tac-toe/

I've created an implimentation based upon what I believe to be correct and I'm getting odd results. The algorithm seems to select the correct move after two incorrect moves. Can anyone see where I've gone wrong? Any help would be greatly appreciated.

Note: The grid is an array[3][3], with 0,0 being top left.

http://pastebin.com/PV8eM1rz

I could not work out the correct way to format code so I've put it in a pastebin link. I hope this is okay.

Thanks again

### #2Álvaro  Members

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Posted 07 May 2014 - 02:34 PM

I don't see any obvious bugs in the code you posted. Can you post the entire program, with some instructions of how to reproduce a situation where it does the wrong thing?

### #3AF1992  Members

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Posted 07 May 2014 - 02:42 PM

I don't have the full program with me at this time, however the only other relivent piece of code besides maybe the basic grid clas (the 3x3 array, and a state check variable (0 = empty, 1 = player one, 2 = player 2) would be the move selection within the main display call back:

BestMoves = MiniMax.MiniMax(Grid1);
if(BestMoves.size() > 0 && UpdateRate == 100){
cout << BestMoves[0] << ", " << BestMoves[1] << endl;
Grid1.Locations[BestMoves[0]][BestMoves[1]].state = 2;

When I set no spaces occupied the code gets stuck in an infinite loop, if I  set up a board where the opponent has 2 in a row, it'll play 2 moves and THEN play the move that blocks the row. Hope this is enough information. thanks

### #4SeraphLance  Members

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Posted 08 May 2014 - 02:20 PM

You're probably going to need to use a debugger for this.

First, try to figure out why the program gets stuck in an infinite loop.  Fix your cases one at a time.

### #5Álvaro  Members

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Posted 08 May 2014 - 03:14 PM

I don't have the full program with me at this time, however the only other relivent piece of code besides maybe the basic grid clas (the 3x3 array, and a state check variable (0 = empty, 1 = player one, 2 = player 2) would be the move selection within the main display call back:

If you have bugs in your code, you don't know what the relevant pieces of code are. You should learn to do your own debugging, but debugging a seriously-recursive algorithm like minimax can be very tricky, and I am willing to help (I think it won't take me long to figure this out, because I have a lot of experience with this type of thing). But you do need to post the whole program.

### #6AF1992  Members

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Posted 08 May 2014 - 03:22 PM

I don't have the full program with me at this time, however the only other relivent piece of code besides maybe the basic grid clas (the 3x3 array, and a state check variable (0 = empty, 1 = player one, 2 = player 2) would be the move selection within the main display call back:

If you have bugs in your code, you don't know what the relevant pieces of code are. You should learn to do your own debugging, but debugging a seriously-recursive algorithm like minimax can be very tricky, and I am willing to help (I think it won't take me long to figure this out, because I have a lot of experience with this type of thing). But you do need to post the whole program.

I would very much appreciate your help on this matter. Its the source of much frustration right now.

Full program Here, Ignore the 'FSM' class

https://www.dropbox.com/s/go3jdxp7rerlvwl/TicTacToe.zip

### #7Álvaro  Members

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Posted 08 May 2014 - 10:50 PM

Sorry, that is a mess that I don't think I can get running in a reasonable amount of time. If you don't know what I am talking about, the fact that your .zip file is about 32 Mbytes in size is a sign that something is terribly wrong.

I encourage you to learn how to write portable C++ without all the clutter. A simple text file is all that's needed.

### #8AF1992  Members

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Posted 09 May 2014 - 01:08 AM

Sorry, that is a mess that I don't think I can get running in a reasonable amount of time. If you don't know what I am talking about, the fact that your .zip file is about 32 Mbytes in size is a sign that something is terribly wrong.

I encourage you to learn how to write portable C++ without all the clutter. A simple text file is all that's needed.

Sorry for the mess, its this size because I decided to upload the whole Visual C++ project, In addition this program uses OpenGL so some of the space is taken up by the Libraries. Thanks for your time regardless of this

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