nil pointers

A case for personal-software suites as a meta-harness feature: the agents build the apps, and the meta-harness runs them.

Building a hosted agents product: the design, the architecture, starting a company, and my agentic workflow.

A list of ideas for interacting with agents.

All 355 lines of a competitive GPT training script, explained line by line for readers who have never built a transformer.

From a hand-coded agent to a system that co-evolves its own code, tasks, and weights.

A proxy that turns a Claude Code session's context into editable frames - delete, compact, offload, and reorder what the model sees.

My PhD origin story.

How frontier models are trained, what RL environments are, and what the job actually looks like at the companies creating them.

Design, architecture, and takeaways from building a meta-harness that supports multi-user, multi-device, and multi-agent conversations.

A detailed walkthrough of the inference pipeline powering self-play for the AlphaZero-style AI behind the Wall Game.

A fictional story set in a world where the sea flows one way.

A playbook for building AlphaZero-style AIs, from architecture to training to deployment.

Introducing Toolkit-X: a free DS&A toolkit with curated BCtCI problems that can be used like a traditional problem list.

How do you coordinate 'trivial' changes across 1440 programs in 5 languages? Lessons from running the BCtCI codebase.

An argument in favor of DS&A interviews.

My open challenge for 'research-level' reasoning LLMs: a deceptively simple special case of stable matching.

Learn how sets & maps are built from scratch, and refine your knowledge of hashing.

Learn how monotonic stacks and queues are two sides of the same idea and how to leverage them in interviews!

A deeper look at this classic grid problem - including some beautiful fractals that unexpectedly appear in the BFS analysis.

A walk through recurrences, memoization, and math tricks -- via Lego castles.

Why context engineering is becoming the name of the game for improving AI apps.

A comprehensive list of all free resources available from Beyond Cracking the Coding Interview, including chapters, problems, tools, and templates.

Learn how this fascinating data structure speeds up graph-related operations.

Peer review has a new scandal: how LLMs are being used to manipulate the process.

Lessons from trying to automate redistricting.

The different approaches to finding the k smallest/largest elements in an array.

JS doesn't have built-in queues, which can be an issue if you have to implement a BFS. Here are the workarounds.

An optimal solution for a graph problem that comes up in the Wall Game.

A linear-time algorithm for a graph problem that comes up in the Wall Game.

An introduction to the Wall Game, my new project.

Designing the DB for the Wall Game.

How would you build a Lichess clone in 2025? My process for picking a tech stack.

The specs of the UI for the Wall Game and renders from frontend generators.

The backstory and thought process behind a fun paper from my PhD.

My grandparents' story during the Spanish Civil War.

A binary search recipe that works for every problem, explained without code.

The exact prompts used to create an interactive 3D torus visualization app with vibe coding.

Exploring the geometry of merging faces.

A problem walkthrough using the concepts from Beyond Cracking the Coding Interview.

A proof that heapify takes linear time without using complex equations.

A curious application of binary search.

Exploring the tradeoffs between lazy and eager implementations of common algorithms.

A comprehensive guide to different implementations of Dijkstra's algorithm, with code.

An extensive list of questions that can be solved with DFS.

Many greedy algorithms can be modified to make local rather than global choices while still producing the same solutions.

A step-by-step guide to understanding and implementing dynamic programming algorithms with practical examples.

A guide to implementing preorder, inorder, and postorder tree traversals iteratively.