Skip to content
CRACKED

The claim

Every efficientalgorithm isbrute forceredundant work

Eighteen kinds of redundancy. Twenty-four mechanisms that eliminate them. Own that mapping and you stop needing to have seen the problem before. This is the instrument that installs it — six rungs, a commit before every hint, and an honest record of where you actually fell off.

Run the drill →See the method
24
mechanisms
18
redundancies
53
DAG nodes
60
forged problems
redundancy_to_mechanism18 × 24
wastere-seeking membership
killHashing
Every edge is a row of the table the grader uses. Hover a node to hold it.

The closed taxonomy of 24 mechanisms: Hashing, Two pointers from the ends, Fast and slow pointers, Fixed sliding window, Variable sliding window, Prefix sums, Binary search on the array, Binary search on the answer, Sorting as preprocessing, Heap, Monotonic stack, Monotonic deque, Linked list, Tree traversal, Trie, Union-find, Segment tree, BFS, DFS, Backtracking, Topological sort, Dijkstra, Greedy, Dynamic programming.

01 The Ladder

Six rungs. You cannot buy your way past one with a hint.

Every hint is priced in commitment: log a falsifiable hypothesis at the rung you are on, or the hint stays shut. Wrong hypotheses are the useful ones — they are what turns a session into a record instead of a feeling.

  1. 01FrameRestate this in your own words. What is the input, the output, and how big can n get?
  2. 02BruteWhat's the dumbest thing that works? Complexity?
  3. 03BottleneckWhat is your brute force doing over and over that it shouldn't have to?
  4. 04LiftWhat kills that specific waste?the hinge
  5. 05InvariantWhat's true after every step, no matter the input?
  6. 06VerifyTrace n=1, empty input, and all-identical. Final complexity?
Rung 3 to rung 4 — naming the waste, then naming the tool that kills it — is the rung nobody teaches explicitly, and the only one that predicts problems you have never seen.

02 The instrument

Three screens, one loop.

01Recognition drill →5 min · 90s an itemName the mechanism and the waste it removes. No coding, no tags, interleaved so context never gives the answer away.both fields requiredserver-timedconfusable pairs weighted
02The Ladder →30 min · core blockSix rungs. No hint is released until a falsifiable hypothesis is logged at the current rung — and a wrong one still counts.Commit Rule enforcedone level, not a leapno skip control exists
03Post-mortem →after every sessionWhat was scheduled and why, what moved, and the failure code with the commit-log evidence that earned it.F1–F6 failure codesquoted evidencedeltas marked pending

03 Under the hood

The rules are enforced where they cannot be edited away.

A tutor that can be talked out of its own pedagogy is a chat window. Every rule this thing claims to have is held by the server, the type system, or a test.

The clock is not the client’s

The countdown is a drawing. Elapsed time comes from a timestamp the server wrote at issuance and re-derives on submit, so a paused, slow, or hostile browser changes the picture and nothing that scores.

The gate is not the disabled attribute

The hint button’s disabled state mirrors a server invariant that throws CommitRuleViolation on the same condition. Deleting the client gate does not open the hint.

A closed taxonomy, typed end to end

Twenty-four mechanisms and eighteen redundancies are const unions. The picker is generated from them, so a taxonomy change is a type error rather than a silent gap in a form.

Mastery is a pure function

EMA with time decay, no Prisma import and no ambient clock — the current time is a parameter. That is what makes the scoring model testable without a database or a fake timer.

Nine agents, each with a refusal contract

Placement, failure analysis, planning, examination, critique, interview. Every one has a written output schema and an explicit list of what it must refuse to say — a coach that leaks the mechanism has failed its contract.

Fifty-one tests, none of them networked

The invariants that matter — the Commit Rule, decay monotonicity, taxonomy closure — are pinned offline. Drill grading falls back to a deliberately conservative offline grader rather than inflating an ungraded answer.

Start where it hurts

Ninety seconds an item. Name the waste, name the tool.

Run the drill →Open the Ladder