# devdelight

> devdelight is the site of Alexander Toder, a software engineer who teaches programming and software engineering on YouTube (youtube.com/@AlexToder): LeetCode and coding-interview solves in Python, C++ and JavaScript with a repeatable method called TEACH, plus system design and tutorials, step by step.

Languages and technologies: Python, C++, JavaScript, TypeScript, Go, Rust, PHP, Java, HTML, CSS; React, Node.js, Express.js, AngularJS, Laravel, CodeIgniter, Zend, Shopify, WordPress; GraphQL, Hasura, REST APIs, MySQL, PostgreSQL, MongoDB, Redis, Memcached; AWS (S3, SQS, EC2, EKS), GCP, Docker, Kubernetes, Helm, Terraform; edge infrastructure, large-scale fleet automation, CI/CD at scale, k3s, event-driven systems, microservices, Linux, Apache; Git, SVN, Jira, Asana, Trello. Shipped: provisioning automation, deployment pipelines, search and pagination APIs, role-based access control, reporting dashboards, voting and coupon platforms, Shopify and WordPress stores.

Code shipped at Meta, Apple, Toyota, Visa, Shipwire, AdBrite, ReTargeter and other San Francisco and Bay Area startups. Highlights: vendor and budgeting software at Apple that manages $90M a year; a C++ parser at Visa handling 1M+ transactions a second; Toyota deployments cut from 45 minutes to seconds with a Kubernetes pipeline; a ReTargeter dashboard taken from minutes to under 15 seconds; founded Development Done Right and led a team of five. Plug and Play alumni. B.S. Computer Science, San Francisco State University. Every video is a whole problem, start to finish, with the thinking left in: the whiteboard, the code, the run and the submit.

## The TEACH method

TEACH is a five-step method for solving a coding-interview problem you have never seen:

- **T · Test cases**: write the inputs that could break the solution before writing any code.
- **E · Explain the solution**: talk through a few approaches out loud, agree on one with the interviewer, then type.
- **A · Apply the algorithm**: write the code.
- **C · Check all cases**: walk the edge cases: empty input, one element, the one nobody tried.
- **H · Highlight the trade-offs**: state the time and space cost and what was given up.

The method with a sample section: https://devdelight.com/teach . The free cheat sheet landing page: https://devdelight.com/cheat-sheet . The full cheat sheet (free, email signup) is at https://devdelight.com/ , section "Want the whole method in fourteen pages?".

## LeetCode and interview problems solved on video

- [LeetCode 864 · Shortest Path to Get All Keys (Hard)](https://www.youtube.com/watch?v=ZfaLyz6O34U): BFS over (row, column, key mask) states, a bitmask for up to 6 keys, in C++ and Python.
- [LeetCode 2461 · Maximum Sum of Distinct Subarrays With Length K (Medium)](https://www.youtube.com/watch?v=vWYKnuLhTYQ): a sliding window of k numbers with a running sum and a frequency map, in C++, with the TEACH method.
- [LeetCode 2460 · Apply Operations to an Array (Easy)](https://www.youtube.com/watch?v=6cQnasapv08): two passes over the same array, no extra memory, in C++, with the TEACH method.
- [LeetCode 269 · Alien Dictionary (Hard)](https://www.youtube.com/watch?v=FZt-XYgqByY): topological sort of letters, solved twice in C++, Kahn's BFS and DFS with three visited states, plus the prefix case that fails.
- [Transpose of a Directed Graph](https://www.youtube.com/watch?v=vWaW7FNZ2hU): a real interview question, BFS to map every node, then reverse every edge, in C++, with the TEACH method.
- [LeetCode 3 · Longest Substring Without Repeating Characters (live stream)](https://www.youtube.com/watch?v=DpDn4hRqwEs): a quick stream in Python and Neovim.

## Links

- [YouTube channel](https://www.youtube.com/@AlexToder): full solves and Shorts.
- [devdelight.com](https://devdelight.com/): the method, the recordings, and an email with new videos, system design breakdowns and AI news.
- [Privacy Policy](https://devdelight.com/privacy.html)
- [Terms of Service](https://devdelight.com/terms.html)