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Chatty ยท Pattern difficulty taxonomy

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1 min read
2026-08-16

30. Our difficulty taxonomy

Every practice question I generate will get classified.

๐ŸŸข Easy โ€” Recognition

You know exactly which tool to use.
Example:
Find the slope through (1,2)(1,2) and (3,6)(3,6).

๐ŸŸก Medium โ€” Transformation

You must recognize and transform the problem.
Example:
A line is perpendicular to another line and passes through a given point. Find its equation.

๐Ÿ”ด Hard โ€” Composition

Multiple concepts interact.
Example:
A probability problem requires counting โ†’ conditional probability โ†’ Bayes.
Or:
A Python question requires nested iteration โ†’ dictionary accumulation โ†’ condition filtering.

โšซ Adversarial

The mathematics/programming itself isn't necessarily difficult.
The difficulty comes from:
  • unusual wording
  • misleading representation
  • hidden constraint
  • boundary case
  • distractor information
  • inverse reasoning
  • subtle Python semantics
These are the questions I particularly want to train you on for Quiz 2.

31. Every pattern will eventually have this anatomy

For example, take Bayes' theorem.

Pattern

Given evidence, infer the probability of the underlying cause.

Step 1 โ€” Identify

What is the hypothesis?
What is the evidence?

Step 2 โ€” Translate

A=hypothesisA=\text{hypothesis}
B=evidenceB=\text{evidence}

Step 3 โ€” Determine requested direction

Are they asking:
P(BโˆฃA)P(B\mid A)
or
P(AโˆฃB)P(A\mid B)
?

Step 4 โ€” Recognize inversion

If the latter, Bayes is likely relevant.

Step 5 โ€” Expand denominator

P(B)=P(BโˆฃA)P(A)+P(BโˆฃAc)P(Ac)P(B) = P(B\mid A)P(A) + P(B\mid A^c)P(A^c)

Step 6 โ€” Substitute

Step 7 โ€” Sanity check

Probability must lie in:
[0,1][0,1]

Step 8 โ€” Generalize

Any problem involving:
prior โ†’ mechanism โ†’ observed evidence โ†’ posterior
belongs to the same family.
That is what I mean by "pattern" in this prep system.

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