manideep3069 / connect4

A game using AI

Connect4-A game using AI

Introduction

Connect Four is a classic two-player game where the objective is to be the first to form a horizontal, vertical, or diagonal line of four discs of your own color. This code implements the Connect Four game using C++ and the minimax algorithm with alpha-beta pruning. The total number of positions possible is 4,531,985,219,092- which is approximately 45 trillion! Using alpha-beta pruning, AI reduces the number of moves it wants to play to maximize its win.

In this README, we will explore the logic behind the code, how it works, the pros and cons of the logic used, suggestions for improvement, and conclude with a summary.

Logic

The code follows a logical structure to implement the Connect Four game. Here are the key components:

Position Class

The Position class represents the game state and provides methods to handle moves, check for winning moves, count the number of moves played, and generate a unique key for each position.

HashTable Class

The HashTable class is used to store position scores. It uses a vector of entries to efficiently store and retrieve scores based on the position's key.

Solver Class

The Solver class implements the minimax algorithm with alpha-beta pruning. It calculates the best move for the computer player by traversing the game tree, evaluating positions, and using the stored scores in the hash table to optimize the search.

Game Logic

The main function handles the game logic. It initializes the game board, reads a sequence of moves, plays the moves, and alternates between user input and computer moves using the Solver class. The game continues until a win condition or a draw is reached.

How it Works?

The code works by representing the game state using a 6x7 game board and maintaining a position object. The main function interacts with the user and the Solver class to determine the next move for both players. The minimax algorithm with alpha-beta pruning is used to evaluate possible moves and select the best one for the computer player.

The game board is updated with each move, and the checkconnect function is used to determine if a winning move is made in a specific column. The position scores are stored in a hash table to avoid recomputing them for already visited positions.

Pros of Logic

The code uses a well-known and effective algorithm, the minimax algorithm with alpha-beta pruning, to determine the best move for the computer player. By using a hash table to store position scores, the code optimizes performance by avoiding redundant calculations. The implementation of the game logic is clear and modular, with separate classes for position handling, hash table operations, and solving the game.

Cons of Logic

The code assumes that the user will input valid moves. It doesn't include extensive error handling or input validation. The code lacks a graphical user interface, limiting the user experience to the console. The evaluation function used in the minimax algorithm could be further improved to make more intelligent decisions. How to Make it Better To enhance the code and the Connect Four game experience, you can consider the following improvements:

Implement input validation to handle invalid user moves gracefully. Develop a graphical user interface to provide a visual representation of the game board and facilitate user interaction. Enhance the evaluation function used in the minimax algorithm to make more strategic decisions, taking into account winning patterns, blocking opponent moves, and creating potential winning opportunities.

Conclusion

This code provides a functional implementation of the Connect Four game using the minimax algorithm with alpha-beta pruning. It demonstrates how to handle game state, calculate optimal moves, and store position scores efficiently. While the code can be enhanced with input validation, a graphical user interface, and a more sophisticated evaluation function, it serves as a solid foundation for further development and improvement.