Connect-Four (Terminal)

A minimal console-based Connect-Four implementation used for course exercises.

Group Members

• Patrick Casseus
• Dante Hurr
• Jaksh Patel

Files

• Board.java — board state and win/draw logic
• Game.java — game loop and user command handling
• Hint.java — simple two-ply hint engine classifying safe/unsafe moves
• Main.java — application entry point
• Move.java — immutable move record (row/col/token)
• MoveStack.java — LIFO stack used for undo functionality
• MyLinkedList.java — tiny linked list used by the hint engine
• Player.java — player descriptor (name and token)
• TurnQueue.java — circular queue to manage player turns
• AIPlayer.java — abstract superclass for AI implementations (easy, medium, hard)
• AVLTree.java — self-balancing tree storing tournament standings sorted by wins and name
• EasyAI.java — basic AI that selects random valid columns
• HardAI.java — advanced AI using recursive minimax search with scoring
• Match.java — stores metadata and outcome for a single tournament match
• MediumAI.java — intermediate AI that blocks wins, favors center, avoids traps
• PlayerManager.java — handles login, registration, profile lookup, and data persistence
• PlayerProfile.java — persistent stats for a registered player, including rolling history
• Tournament.java — manages round-robin scheduling, match queue, and match execution
• TournamentEntry.java — wrapper for a player's tournament stats (wins, losses, name)
• TournamentStats.java — node wrapper used by AVLTree for sorting and output

Prerequisites

• Java 11+ (javac and java on PATH)
• macOS / Linux / Windows terminal

Compile

From the project directory (where the .java files live) run:

javac connectfour/*.java

This will produce .class files next to each source file.

Run / Play (interactive)

Start the game:

java connectfour.Main

The game runs interactively in the terminal. Prompts are displayed for the current player.

Available commands (type at the prompt):

• <column number> — type a number between 0 and 6 to drop your token
• undo — undo the last move (restores the board and the turn order)
• hint — compute and print a simple hint: recommended, safe and unsafe moves
• board — reprint the current board snapshot
• restart — clear the board and start a new game (player order is preserved)
• help — show the help menu
• quit — exit the game

Newer Commands (type at the prompt):

• register <name> — create a new player account
• login <name> — login as an existing player
• logout — logout of the current session
• whoami — show the current logged-in user
• profile <name> — show stats and history for a user
• leaderboard top N — show top N players by win count
• game start human [X O] — start human vs human
• game start ai <level> — start human vs AI (easy, med, hard)
• tournament create <id> <p1,p2,...> — create a tournament
• tournament start <id> — schedule all matches
• next — play the next match in the queue (AI vs AI)
• tournament standings <id> — show AVL-based standings

Notes on gameplay and features

• Two players are configured by default: Player 1 uses X, Player 2 uses O.
• The board default is 6 rows x 7 columns and connect-4 win condition.
• The hint engine is a shallow two-ply simulation that detects immediate opponent wins after your candidate move (it does not perform deep search).
• The undo feature reverses the last move(s); in AI games, both the player and AI moves are undone.
• The hint engine avoids unsafe moves that allow immediate losses on the opponent’s next turn.

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AI difficulty levels include:

• Easy — selects random valid columns.
• Medium — blocks wins, prefers center, avoids traps.
• Hard — uses recursive minimax search with a static evaluation function.

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• Player accounts persist stats across sessions, including total and AI-specific win/draw/loss counts.
• Each player profile keeps a rolling history of their last 10 game outcomes.
• Tournaments simulate round-robin play between players using AI.
• Tournament standings are stored in an AVL tree and ranked by win count (descending), then player name (ascending).