Medium

Design Blackjack and a Deck of Cards Object-Oriented Design Interview

Design a reusable deck of cards and a single-round Blackjack game: cards, suits and ranks, deck shuffle/deal, hand scoring with flexible ace values, player and dealer turns, and terminal outcomes (blackjack, bust, win/lose/push).

1. Problem Statement

Design a reusable deck of cards and a single-round game of Blackjack on top of it. Cover cards, the deck's shuffle and deal, hand scoring (including aces that can count as 1 or 11), the player and dealer turns, and how a round is settled. Start by clarifying scope and the core objects.

2. Live Coding Format

Work in the provided coding workspace while explaining your decisions to the live interviewer. Validation may use inline tests, examples, comments, or a verbal walkthrough.

3. Key Focus Areas

  • 1
    Card/Suit/Rank value objects and Deck shuffle/deal
  • 2
    Hand scoring with flexible ace values and blackjack detection
  • 3
    Round lifecycle: deal, hit/stand, dealer policy, settle
  • 4
    Configurable dealer policy and optional betting value object

4. What Strong Candidates Should Demonstrate

  • Model Card, Suit, Rank, and Deck as a reusable, well-encapsulated component.
  • Compute blackjack hand values correctly with flexible ace handling.
  • Separate deck/card mechanics from game rules and dealer policy.
  • Model the round lifecycle and terminal outcomes (blackjack, bust, win/lose/push).

Want interactive feedback?

Practice this problem in the live coding workspace while the interviewer probes your clarification, implementation, trade-offs, and validation.

Continue to Dashboard

Core Concepts

Object-Oriented DesignDomain ModelingGame ModelingValue Objects

Continue preparing

Build a complete software engineer mock interview plan

Related Object-Oriented Design

Design a Car Rental System

Design a car rental domain model covering vehicle categories and vehicles, branches, customers and drivers, a rental date range, rate-based quotes, reservations, pickup rental agreements, and return inspection with extra charges — preventing overlapping rentals of the same vehicle.

Related Object-Oriented Design

Design a Hotel Management System

Design a hotel domain model covering room types and rooms, guests, a half-open date-range value object, the reservation lifecycle, room assignment, check-in/out, and a charges folio, while preventing overlapping bookings on the same room.

Related Object-Oriented Design

Design a Cricket Information Platform

Design a cricket scoring domain model covering teams and players, a match, innings, overs and deliveries, batting and bowling scorecards, extras and wickets, striker rotation, over completion, and match results for a configurable limited-overs format.

Related Object-Oriented Design

Design a Library Management System

Design a library that models catalog titles versus physical copies, members and librarians, checkout/return/renew/reserve flows with loan due dates, an overdue fine policy, and notifications as a boundary.