Design an Elevator System

Easy

+150 XP

Low Level DesignLLDSystem DesignOOPState PatternObserver PatternStrategy

Design a smart elevator control system for a high-rise building with multiple elevator cars. The system should intelligently dispatch elevators to minimize wait times, handle both external (floor buttons with UP/DOWN direction) and internal (cabin buttons) requests, and support concurrent operations.

Key requirements:

The system should have a central controller to manage all elevators in the building
Each elevator should have distinct states (idle, moving up, moving down) with different behaviors in each state
The system should support different algorithms for selecting which elevator to assign to a request (e.g., nearest elevator, least loaded), and these algorithms should be easily swappable
Multiple displays and other components need to be notified when elevator states or positions change
The system must handle concurrent requests from multiple users safely without race conditions or data corruption

🛗 Smart Elevator Dispatcher

Status: System Idle

IDLE

Floor Controls

Floor 6

Floor 5

Floor 4

Floor 3

Floor 2

Floor 1

System Logs

What You'll Build

FR1: The building has several elevators, and each elevator can go to all floors.
FR2: People should be able to request an elevator from any floor (external request) and choose the floor they want to go to once inside (internal request).
FR3: The elevator system should use a smart dispatching strategy to select the best elevator for each external request, considering factors like distance and direction.
FR4: Each elevator should be able to handle multiple ride requests simultaneously and process them efficiently.
FR5: Elevators should process requests in the current direction before reversing direction to minimize travel distance.
...and more

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