Board, Player, Game classes in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Identify the primary responsibility of the Game class

In a simple board game design, which of the following best describes the main responsibility of the Game class?

A Manage the overall game flow, including turns and win conditions

B Store the positions of pieces on the board

C Represent a player with their attributes and actions

D Handle user input and display the game interface

💡 Hint

Think about which class controls the sequence of play and decides when the game ends.

The Game class is responsible for managing the game flow, such as alternating turns between players and checking if someone has won. The Board stores piece positions, and Player represents individual players.

❓ Architecture

intermediate

Choose the best design for Player and Board interaction

Which design best supports a Player interacting with the Board in a turn-based game?

A Board directly modifies Player attributes during a move

B Player has a method to make a move that updates the Board state

C Game class modifies Player and Board independently without interaction

D Player and Board communicate only through a global variable

💡 Hint

Consider which class should initiate changes to the board during a player's turn.

The Player should have a method to make a move that updates the Board state. This keeps responsibilities clear and interactions controlled.

❓ scaling

advanced

Scaling the Board class for large games

For a game with a very large board (e.g., 1000x1000 cells), which approach best optimizes memory and performance?

A Use a sparse data structure to store only occupied cells

B Create a separate Board instance for each player

C Store all cells in a 2D array regardless of occupancy

D Store only the last move and reconstruct board state on demand

💡 Hint

Think about how to avoid wasting memory on empty cells.

Using a sparse data structure stores only occupied cells, saving memory and improving performance for large boards.

❓ tradeoff

advanced

Tradeoff between Player class complexity and Game class control

What is a key tradeoff when giving the Player class more decision-making logic versus centralizing logic in the Game class?

A Centralizing logic in Game always improves performance

B More logic in Player reduces code reuse across different games

C More logic in Player increases modularity but can complicate coordination

D Centralizing logic in Game makes Player classes harder to test

💡 Hint

Consider how distributing logic affects modularity and coordination.

Giving Player more logic improves modularity but can make coordinating game flow harder. Centralizing logic simplifies coordination but reduces modularity.

❓ component

expert

Estimate capacity for concurrent games in a server

A server runs multiple concurrent games, each with 2 players and a 10x10 board. Each game requires 1MB memory and 5ms CPU per turn. The server has 16GB RAM and 2GHz CPU with 8 cores. Estimate the maximum number of games it can handle simultaneously without performance degradation.

A About 10,000 games limited by memory

B About 12,800 games limited by CPU

C About 16,000 games limited by memory

D About 3,200 games limited by CPU

💡 Hint

Calculate max games by dividing total resources by per-game usage, then find the bottleneck.

Memory allows 16,000 games (16GB / 1MB). CPU per core can handle 200 turns per second (1000ms/5ms). With 8 cores, total 1,600 turns per second. Assuming 1 turn per game per second, CPU limits to ~1,600 games.