Posts (238+)

Browse the full archive. Use topics in the sidebar to explore by tag.

September 2026

Backtracking:Search With Undo When the Next Choice Depends on the Last

Choose, recurse, undo: search a decision tree with pruning when the next pick depends on the path — not a second knapsack table.

Design Patterns

Composite:Treat Trees of Objects as One

Replace nested loops over Outdoor / Hiking / SKUs with a CatalogNode tree so a category and a single product both answer subtotal(), and OrderProcessor still charges one payable.

Design Patterns

Proxy:Stand In for an Object You Cannot Touch Directly

Put a PaymentGateway proxy in front of a slow SDK so OrderProcessor still calls charge, while lazy init, an auth check, and a last-result cache decide whether the real gateway runs.

Linux

Linux strace:See What a Stuck Process Is Waiting On

Hands-on strace recipes — attach to a PID, follow children, filter syscalls, and read the wait that logs never mentioned.

Algorithms

Interval Scheduling:Always Take the Finish That Frees the Room Soonest

Pick a maximum subset of non-overlapping intervals by earliest finish time — greedy that throws ranges away, not merge-intervals.

Design Patterns

Command:Turn a Request into an Object

Turn charge, refund, and capture into Java objects you can queue, retry, undo, or audit — without wrapping a one-shot process() in ceremony.

Linux

Linux tar and gzip:Archive, Compress, and Restore Without Corrupt Surprises

Hands-on tar and gzip recipes — create an archive, inspect it before extract, compress with gzip, and restore without clobbering the wrong tree.

Design Patterns

Facade:One Simple Front for a Messy Subsystem

Hide checkout’s discount, payment, fraud, and tax conversation behind one CheckoutFacade.place(Order) so controllers stop assembling the subsystem.

Java

Primitive Types in Patterns:instanceof and switch Without the Wrapper Dance

Try JEP 532 in JDK 27: use primitive patterns with instanceof, switch directly on long, float, double, and boolean, and reject lossy conversions without hand-written casts.

Linux

Linux cut, sort, uniq, and tr:Shape Text Before You Pipe to awk

Hands-on text-prep recipes — slice columns, sort keys, count uniques, and translate characters before you reach for awk or sed.