Zipline·Software Engineer·Technical Phone Screen·Senior

SeniorPrefer not to say

May 2026Remote

Summary

Zipline gave me a system design coding question that was basically 'build a checkers simulator OOP style' and I spent most of the time second-guessing my class hierarchy. Solid technical round, nothing behavioral, just deep in the weeds on design and implementation.

Questions Asked (1)

Design and partially implement an object-oriented simulator for a two-player checkers-like board game, covering class design, public APIs, core algorithms, and edge case handling.

System DesignAlgorithms & Data StructuresTechnical Trade-offs

Author's notes

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then outline a class hierarchy with clear separation of concerns (board, pieces, rules, players, game controller). Walk through the public APIs and core algorithms (move validation, capture logic, win detection) before diving into a partial implementation of one or two key methods, explicitly addressing edge cases and trade-offs.

Pro tip: Demonstrate test-driven thinking by describing how you would unit test the move validator and capture logic, and mention how you'd extend the design for variants (e.g., different board sizes or rules) without modifying existing classes.

1. Clarify requirements and constraints

Ask about board size, piece types, movement rules, win conditions, and whether AI or network play is needed. Confirm the scope of 'partially implement' (e.g., focus on core move validation).

2. Design class structure and public APIs

Define classes like Board, Piece, Player, Move, Game, and RuleEngine. Specify key public methods (e.g., Board.getPiece, Game.makeMove, RuleEngine.isValidMove) and their signatures.

3. Outline core algorithms

Explain move generation, validation (including captures and multi-jumps), turn management, and win/draw detection. Discuss data structures (e.g., 2D array for board) and algorithmic complexity.

4. Partially implement a critical component

Choose one or two methods (e.g., isValidMove or applyMove) and write clean, well-commented code. Highlight edge cases like boundary checks, forced captures, and promotion.

5. Address edge cases and trade-offs

Discuss handling of invalid moves, simultaneous captures, stalemate, and extensibility. Mention trade-offs between simplicity and flexibility (e.g., rule engine vs. hardcoded rules).

Key Points to Mention

Separation of concerns: board state, piece behavior, rule validation, and game flow should be distinct classes.
Public API design: methods should be intuitive, minimal, and return meaningful results (e.g., MoveResult with success/failure and reason).
Move validation algorithm: check direction, occupancy, capture availability, and multi-jump sequences.
Edge cases: board boundaries, no legal moves, forced captures, piece promotion, and draw conditions.
Extensibility: use strategy or template patterns for rule variants without modifying core classes.
Testing: unit tests for move validation, capture logic, and win detection to ensure correctness.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.