Don’t just watch it move
- 1Before stepping, predict the next comparison, pointer move or state update.
- 2Read the explanation and identify the invariant that remains true.
- 3Change the input, then solve the concept quest without guessing.
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Class 8 · DSA · Enrichment
Recursion & call stacks
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DSA enrichment · Learning goals & preparation
By the end, you can…
- Explain A base case stops expansion; returning solves the suspended calls.
- Trace a small input and connect each operation to the algorithm’s rule.
- Explain the implementation’s time and space cost and solve its mission.
Useful preparation: Reading arrays, indexing from zero and following step-by-step instructions. Suggested previous stop: Palindrome / strings.
DSA uses suggested Foundation (Class 8), Builder (Class 9) and Advanced (Class 10) levels. It is an enrichment pathway.
Foundations · Foundation
Recursion & call stacks
result4
Ready. Step through the algorithm and explain each change.
factorial(n)if n <= 1: return 1smaller = factorial(n−1)return n × smaller
Recursion & call stacks quest
Explain the idea, read its complexity, then solve a hands-on or trace mission with your current input.
01 · UnderstandFind the invariant→02 · AnalyseThink about cost→03 · SolveUse the model
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From foundations to advanced patterns
The library covers core DSA techniques with bounded teaching examples. Foundation, Builder and Advanced describe learning progression, rather than a school-class syllabus. Snapshots are stored for playback and are excluded from algorithm-space labels.
Further study: MIT Introduction to Algorithms ↗