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Ace Machine Coding rounds at top tech companies. Master production-grade class structures, concurrency synchronization, SOLID principles, and design patterns.
Confirm functional scope, edge cases, input formats, and in-scope vs out-of-scope constraints.
Define core entities, attributes, enums, interfaces, and relationships (Composition > Inheritance).
Apply Strategy for algorithms, Factory for object creation, and State for lifecycle transitions.
Write clean, extensible, modular code with clear method signatures and zero magic numbers.
Add thread safety using `ReentrantLock`, `ConcurrentHashMap`, or `AtomicInteger`.
Multi-floor parking lot supporting different vehicle types (Compact, SUV, EV, Motorcycle), automated billing, and spot allocation strategies.
High-concurrency in-memory Key-Value cache with configurable eviction policies (LRU, LFU, FIFO) and thread-safe operations.
Rate limiting library for API endpoints supporting Token Bucket and Leaky Bucket algorithms with sub-millisecond thread safety.
Multi-elevator scheduling algorithm handling internal/external requests, floor direction states, and dispatching strategies (LOOK/SCAN).
Group expense tracking system supporting exact amounts, percentages, and bill simplification algorithms to minimize net transactions.
Cinema ticketing platform supporting theater layouts, seat reservation holds, concurrent booking locks, and payment timeouts.
Multiplayer board game supporting customizable board sizes, multiple dice, snakes, ladders, and win condition evaluation.
Scalable N x N Tic-Tac-Toe supporting dynamic board size, win evaluation in O(1) time per move, and bot players.
State-driven vending machine handling Ready, Idle, CoinInserted, Dispensing, and OutOfStock state transitions cleanly.
ATM banking interface with cash dispenser chain of responsibility ($100, $50, $20 notes), PIN authentication, and card reader.
Object-oriented Chess game with Piece movement validation (Pawn, Knight, Rook, Queen, King), Check/Checkmate logic, and move undo history.
Hotel booking platform managing room types (Deluxe, Suite), housekeeping status, guest reservations, and checkout invoicing.
Book inventory management supporting barcode scanning, member reservations, fine calculations, and overdue notifications.
Logger framework supporting log levels (DEBUG, INFO, ERROR), chain of handlers (Console, File, Cloud), and async buffer flushes.
Notification engine delivering messages via Push, SMS, and Email with template interpolation, retry mechanisms, and rate limits.