DSA TrainerYou understood the video. Then the next problem happened.
Following an explanation and producing one are different skills, and interviews only test the second. These courses make you predict the move before every reveal, on every concept, until the patterns are yours: data structures and algorithms first, system design when you are ready.
37 units · 118 guided problems · 56+ AI-bug drills · progress saved
Try the method · 10 seconds
Two Sum: find the pair in a list that adds up to 100. Your first instinct?
Compare every pair until one hits
Everyone starts here, and it works. It checks every pair, so the interviewer's next word is "faster?". Knowing why it is slow is what points at the fix.
Sort the list first, then look around
Real instinct, and sorting plus two pointers genuinely solves it. You paid the sort for it, and you lost the original positions, which this problem asks for. Close.
At each number, ask: have I already seen the one I need?
That reframe is the whole pattern. Remember what you have passed, check for 100 minus current in one step. The structure that does that is a hash map, and it is unit 2.
You committed to a guess before the reveal. That moment, on every concept in both courses, is why this transfers to problems you have never seen.
Pick your course
Same method in both · progress savedYou’re not signed in. Your progress here won’t be saved.
Course 1 · Data structures & algorithms
DSA Foundations
From 'what is a hash map' to solving problems you have never seen. Learn each concept, drill it, pass the test, then solve real problems with the guidance fading step by step.
- 17 units in one ordered path, Big-O through dynamic programming
- 118 guided problems with a hint ladder that never dumps the answer
- 56 "Spot the AI's bug" drills for the new AI-assisted round
Course 2 · System design
System Design Foundations
The interview that now shows up in new-grad and mid-level loops. Learn the building blocks through when-to-use judgment: when to reach for a cache, a queue, a replica, and why.
- 20 building-block units: caching, queues, sharding, and friends
- Judgment over diagrams: know when to reach for each piece, and defend it
- Prediction-first checkpoints and graded tests in every unit
One loop, repeated until it's yours
Every unit in both courses runs the same five moves. The order matters: the prediction comes before the teaching, because that is what makes the teaching stick.
- 1
Predict
Read a concrete scenario and commit to a call before any reveal.
- 2
See why
The reveal explains why your answer was right, or exactly which trap you walked into.
- 3
Drill it
Applied drills: same judgment, new scenarios, until the trigger is automatic.
- 4
Pass the test
A graded test gates the unit. No skimming your way to 'done'.
- 5
Use it for real
Real problems with the guidance fading step by step, until you barely need it.
Everything a CS degree teaches about interviews, without the degree
Both courses are sequenced start to finish, so you never have to wonder what to learn next. The counts below grow as new units land.
Built for people who can code but freeze on interview problems
Bootcamp grads
You can ship an app, and none of that helps when a stranger says 'reverse a linked list'. The DSA path starts at the actual beginning and never assumes CS vocabulary.
CS students (yes, WGU counts)
You passed the course; producing the pattern under pressure is a different muscle. The drills and cold-read capstones train recall, not recognition.
Self-taught developers
Years of real experience, zero formal DSA. The path fills the gaps in order, and System Design turns what you already know from work into interview answers.
Common questions
Which course should I start with?
Most interview loops still weight the coding rounds heaviest, so start with DSA Foundations. Add System Design once you are past the DSA basics, or right away if a loop with a design round is coming up. Both courses save progress to the same account, so you can run them in parallel.
Is this free?
Both courses are free to start. Every DSA lesson is free to read, and the first DSA modules are fully free including drills, tests, and real problems. The first two System Design units are fully free as well. Premium unlocks everything after: the rest of the System Design course plus all DSA practice and testing.
How is this different from watching course videos?
Videos feel like learning because following an explanation is easy. Interviews test whether you can produce the idea yourself, which is a different skill. Every lesson here makes you commit to an answer before showing you why, because a prediction that turns out wrong is where the learning actually happens.
Do I need to be good at math or have a CS degree?
No. The courses assume you can write basic code in any language and nothing else. Every concept opens with a concrete scenario before any terminology, and Big-O is built up from counting steps, not formulas.
How long does each course take?
DSA Foundations is 17 units with 118 guided problems; most people run one unit plus its problems in a few evenings. System Design Foundations is 20 shorter units you can finish in a couple of weeks of consistent sessions. Both are self-paced with progress saved.
Read the first lesson free. Predict your first move in the next two minutes.
No card, no trial clock. Both courses are free to start; premium unlocks the rest when you want it.