Tic-Tac-Toe

3x3 Tic-Tac-Toe console game (human vs computer, turn by turn) written in Scala.

Info

The human player may choose:

• his/her own mark (x or o)
• which player makes the first move (human or computer)
• the difficulty of the computer (easy or hard)
• to start a new game after a game has ended

Computer Algorithms

The easy computer just randomly selects a free position on the board and thus is easy to beat (in most cases).

The hard computer is based on the NegaMax algorithm (which is a slight modification of the MiniMax algorithm) and thus is unbeatable. Here is a very illustrative explanation of the MiniMax algorithm by Patrick Winston.

The NegaMax variation is simply based on the idea that

max(a, b) = -min(-a, -b)

and thus there is no need to explicitly distinguish in which level the evaluation step of a move takes places. This is done by a value called level which equals max=1 for the computer's turn or min=-1 for the player's turn.

Project Setup

1. Clone this repository to any destination path you want (for example '~/Downloads/tic-tac-toe').

2. Open terminal and navigate to this directory:

   $ cd ~/Downloads/tic-tac-toe
   

3. Compile project:

   $ sbt compile
   

4. Run tests:

   $ sbt test
   

5. Run tic-tac-toe game:

   $ sbt run
   

Preview

The computer🤖 makes a decision...
The computer🤖 chose the move row = 1, column = 3
 x | x | o 
-----------
   | o |   
-----------
   |   |   

Have fun! :)