Data Structures & Algorithms in Practice

A coach that teaches by asking — not by lecturing

The Lighthouse Coach is an AI Socratic coach built on Cognosco Learning's Data Structures & Algorithms in Practice course, in the Personal Effectiveness & Well-Being category. It does not play videos at you. It holds a conversation: it asks you a question, listens to your answer, names the misconception it hears, affirms what you got right, and asks the next question — the way a great coach works in the room.

Every live system is, underneath its screens and buttons, a set of choices about how data is held and how it is found. Those choices decide whether a lookup takes a blink or a minute, whether a queue drains or drowns, whether a cache helps or misleads, and whether a system that works beautifully for a thousand records still works at a million. Canonical algorithm theory belongs to its companion course in this library — this course is the applied companion: the decisions a working engineer makes when a structure must serve real users, real data, and real load.

You learn to choose from the question. Name the operations a feature truly needs and how often each runs; read the cost of each candidate structure in those operations; set a budget for that cost before building; keep hash tables, caches, queues, and sorted structures fast under real load; and use trees, heaps, graphs, and indexes to serve order, priority, routes, and dependencies.

Then you keep it honest in production. Measure performance and find the real bottleneck instead of optimising the wrong thing; price approximate answers with their error bounds stated; keep shared structures safe when many threads touch them at once; persist writes so they survive a crash; degrade gracefully when the ideal path fails; and record and defend every structure decision, including its limits and its fallback.

It works in two movements. First, Module 1 — Choosing and Keeping Structures Fast — work through Concepts 1–9, finishing with The Structure Decision Record; then, Module 2 — Order, Storage, and Survival at Scale — work through Concepts 10–18, finishing with The Peak-Load Storage and Resilience Design.

Both capstones produce real artifacts — The Structure Decision Record, a written decision record for a live service of Sagebrush Route Co., the fictional regional parcel network every concept works on, with budgets, failure modes, and measurable revisit triggers; and The Peak-Load Storage and Resilience Design, the same network designed for peak season and defended in writing, closing with its six-field structure review record.

The numbers discipline is part of the course. No figure is presented as market data or as a statistic about any real company: every worked count is small, chosen so you can recompute it by hand — and one honesty rule governs the whole book: a structure is a promise about cost, and a promise you have not measured is a guess.

The course is self-paced and always on — roughly 30 minutes per concept, about 9 hours in full, taken in as many sittings as you like. You can type your answers, or talk out loud: the Voice Coach speaks its questions and listens to your spoken replies. Learners who already know the material can test out concept by concept.

This is the two hundred and tenth course in The Lighthouse Signature Series — the online counterpart to the one-day, in-person learning Cognosco Learning has delivered since 2002.