# melvinzhang/rule-based-ttt

Investigation of simple rule based Tic-Tac-Toe playing programs
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# Analysis of Simple Tic Tac Toe AIs

Code for the "Design your own Tic-Tac-Toe AI activity" developed during the Hour of Code SG 2014, held at the Singapore Science Center.

Participants code their own AI (by giving a preference order for each square) and we will play against it and discover its strengths and weakness.

Then we show how programs can be used to automate the tedious task of testing the AI. We'll use the code in the repo to find counterplays and quantitatively compute the strength of the AI.

The code can also be used to enumerate all 9! possible programs. There are some interesting ones, such as [[2 6 8] [5 9 1] [3 4 7]], that only has a single way to win it when it goes first.

# Model for a simple Tic Tac Toe AI

Consider a class of Tic Tac Toe AI that follows the following rules and executes the first one that applies

1. win if I have two symbols in a row
2. block if opponent has two symbols in a row
3. place in the lower left corner
4. place in the upper left corner
5. place in the upper right corner
6. place in the lower right corner
7. place in the center
8. place in the bottom edge
9. place in the left edge
10. place in the right edge
11. place in the top edge

Rules 3 - 11 can be represented as follows:

``````   |   |
2 | 9 | 3
---|---|---
7 | 5 | 8
---|---|---
1 | 6 | 4
|   |
``````

Rules 1 and 2 are fixed, but rules 3 - 11 can be reorderd. There are a total of 9! (362880) different AIs.

# Usage

rule-based-ttt/check takes as input a matrix representing rules 3 - 11 and output the number of win/lose/draw games against a player which tries all possible moves.

Requires: leiningen

``````lein repl
=> (check [[2 9 3] [7 5 8] [1 6 4]])
Testing AI as first player
win: 9
lose: 2
draw: 8
Testing AI as second player
win: 36
lose: 42
draw: 121
``````