Getting Ready: Snake and Ladder

Snake and Ladder is one of the oldest board games in the world — originating in ancient India as Moksha Patam (a game used to teach morality, where ladders represented virtues and snakes represented vices). Today, it's played by millions digitally through apps like Ludo King, MPL, and countless online multiplayer platforms.

From an engineering perspective, the Snake and Ladder game engine must handle several interesting challenges: managing turn order across multiple players, applying board effects (snakes and ladders) that alter a player's position, enforcing win conditions, and supporting configurable board layouts. Digital implementations by companies like Zynga, MPL, and Dream11 power real-money gaming — meaning correctness in the game loop is not optional.

As an LLD interview problem, Snake and Ladder is a favorite for testing foundational OOP skills without the overwhelming complexity of harder systems. Interviewers use it to evaluate whether you can model an abstract class hierarchy (the shared structure between snakes and ladders), manage game state cleanly, and write a game loop that's easy to extend. It's often the first "game engine" problem candidates face, making it a perfect stepping stone to Chess (DP21) and other complex game designs.

By working through this design problem, you will:

• Model an abstract class hierarchy — design a BoardEntity base class with Snake and Ladder as concrete subclasses, practicing inheritance and polymorphism
• Implement queue-based turn management — use a queue (deque) to cycle through players, which is cleaner and more extensible than index-based tracking
• Apply the Template Method pattern — define a game turn algorithm skeleton with customizable steps for board entity effects
• Design a complete game loop — from dice rolling through position updates, entity effects, and win detection
• Create a UML class diagram — model all classes, attributes, methods, and relationships derived from requirements
• Draw an activity diagram — visualize the game flow including decision points for snakes, ladders, and win conditions
• Write complete implementations — in both Python and Java, with realistic driver examples

Before starting this problem, make sure you're comfortable with:

• Inheritance & Polymorphism — how abstract base classes define contracts that subclasses fulfill (Fundamentals S3)
• OOP Relationships — the difference between Composition, Aggregation, and Association, and when to use each (Fundamentals S4)
• UML Class Diagrams — how to read class boxes, relationship arrows, and multiplicities (Fundamentals S5)
• Template Method Pattern — defining an algorithm skeleton in a base class with overridable steps (Fundamentals S12)
• Queue data structure — FIFO ordering for turn management (standard library knowledge)

If you've completed DP2 (Tic Tac Toe), you already have experience with game loops and board modeling. Snake and Ladder introduces a new challenge: board entities that modify player state — something Tic Tac Toe didn't have.

We will design: The core game engine — the Board with configurable snakes and ladders, Player management with queue-based turns, a Dice roller, and the Game controller that orchestrates the full game loop from start to finish.

We will NOT design: Multiplayer networking, user authentication, leaderboards, UI/frontend rendering, database persistence, or real-money wagering systems. This is a Low Level Design (object-oriented) exercise — we focus on the class structure, relationships, and game logic, not infrastructure.

Difficulty: Easy — this problem has a small class count (6-8 classes), straightforward state management, and no concurrency concerns. It's an excellent second design problem after Tic Tac Toe, introducing abstract hierarchies and entity-based board effects.