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Class 9 · DSA · Enrichment

Counting sort

Interactive explanation Gamified quiz, feedback & rewards

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DSA enrichment · Learning goals & preparation

By the end, you can…

  • Explain A small integer range can replace pairwise comparisons with counting.
  • 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: Heap sort.

DSA uses suggested Foundation (Class 8), Builder (Class 9) and Advanced (Class 10) levels. It is an enrichment pathway.

Sorting · Builder

Counting sort

Ready. Step through the algorithm and explain each change.

  1. allocate counts for value range R
  2. count each input value
  3. for value = 0 to R−1
  4. write value count[value] times
  5. return reconstructed array

Up to 12 integers. Apply input to rebuild the trace and restart this topic’s quest.

A deliberate practice loop

Don’t just watch it move

  1. 1Before stepping, predict the next comparison, pointer move or state update.
  2. 2Read the explanation and identify the invariant that remains true.
  3. 3Change the input, then solve the concept quest without guessing.
About this pathway

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 ↗