Tag
#design-patterns
7 articles tagged design-patterns.
Design Patterns Explained: The Gang-of-Four Patterns That Show Up in LLD Rounds
Design patterns explained for interviews and low-level design: the Gang of Four patterns — factory, builder, singleton, adapter, decorator, strategy, observer, state, template method, command.
Bar Graph Library LLD: A Chart Is a Function from Numbers to Pictures
A low-level design walkthrough of a bar graph chart library: series data, a linear scale with nice ceilings, and pluggable renderers that draw the same chart in the console and as SVG.
File System LLD: The Composite Pattern's Home Turf
A low-level design walkthrough of an in-memory file system: files and directories behind one Node interface, path resolution as a walk, recursive size via the Composite pattern — fully implemented.
Logging Library LLD: Build log4j's Skeleton in One Sitting
A low-level design walkthrough of a logging library: ordered levels, a cheap threshold gate, formatters, appenders as a Strategy, and the complete implementation of the log4j shape.
Chess LLD: Scope Like a Senior, Move Like a Strategy Pattern
A low-level design walkthrough of chess: scoping the unbuildable, one movement rule per piece via the Strategy pattern, a shared path-clear helper for sliding pieces, and the complete implementation.
Vending Machine LLD: Where the State Pattern Earns Its Keep
A low-level design walkthrough of a vending machine: coins, inventory, the can't-make-change trap, and when design patterns earn their keep — the honest path from if-checks to the State pattern.
A Rookie's Guide to LLD: The Parking Lot and the Pattern Cheat Sheet
How to approach any low-level design interview: turn requirements into classes, methods, and state machines — the parking lot classic, fully built — plus a cheat sheet for picking design patterns.