Scala algorithm: Reshape a matrix

Published

Algorithm goal

Turn an m-by-n matrix into an n-by-m matrix, retaining the order of the elements. For example:

123
456

Becomes:

12
34
56

Test cases in Scala

assert(reshapeMatrix(Vector.empty) == Vector.empty)
assert(reshapeMatrix(Vector(Vector(1))) == Vector(Vector(1)))
assert(reshapeMatrix(Vector(Vector(1, 2))) == Vector(Vector(1), Vector(2)))
assert(
  reshapeMatrix(Vector(Vector(1, 2), Vector(3, 4))) ==
    Vector(Vector(1, 2), Vector(3, 4))
)
assert(
  reshapeMatrix(Vector(Vector(1, 2, 3), Vector(4, 5, 6))) ==
    Vector(Vector(1, 2), Vector(3, 4), Vector(5, 6))
)

Algorithm in Scala

3 lines of Scala (version 2.13), showing how concise Scala can be!

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Explanation

In Scala this is straightforward: flatten the whole matrix, and then group the elements into chunks of length of the height of the matrix (.grouped). (this is © from www.scala-algorithms.com)

Scala concepts & Hints

  1. View

    The .view syntax creates a structure that mirrors another structure, until "forced" by an eager operation like .toList, .foreach, .forall, .count.


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Explore the 21 most useful Scala concepts

To save you going through various tutorials, we cherry-picked the most useful Scala concepts in a consistent form.

  1. Class Inside Class
  2. Class Inside Def
  3. Collect
  4. Def Inside Def
  5. Drop, Take, dropRight, takeRight
  6. foldLeft and foldRight
  7. For-comprehension
  8. Lazy List
  9. Option Type
  10. Ordering
  11. Partial Function
  12. Pattern Matching
  13. Range
  14. scanLeft and scanRight
  15. Sliding / Sliding Window
  16. Stack Safety
  17. State machine
  18. Tail Recursion
  19. Type Class
  20. View
  21. Zip

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