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Added strand sort #1982

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Added strand sort #1982

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@mateuszz0000
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mateuszz0000 commented May 14, 2020

Describe your change:

I didn't find strand sort (https://en.wikipedia.org/wiki/Strand_sort) implemenation so here it is.

  • Add an algorithm?
  • Fix a bug or typo in an existing algorithm?
  • Documentation change?

Checklist:

  • I have read CONTRIBUTING.md.
  • This pull request is all my own work -- I have not plagiarized.
  • I know that pull requests will not be merged if they fail the automated tests.
  • This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
  • All new Python files are placed inside an existing directory.
  • All filenames are in all lowercase characters with no spaces or dashes.
  • All functions and variable names follow Python naming conventions.
  • All function parameters and return values are annotated with Python type hints.
  • All functions have doctests that pass the automated testing.
  • All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
  • If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.
@mateuszz0000 mateuszz0000 mentioned this pull request May 14, 2020
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import operator


def strand_sort(arr: list, solution: list, _operator: callable):

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@cclauss

cclauss May 14, 2020

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This sort would be easier to use (and test) if it returned a list instead of requiring the caller to allocate and pass in a solution list. It would also be cool if strand_sort() was defined to work like the Python builtin sorted() which has an optional reverse parameter that defaults to False. We don't need to support the key parameter of sorted() but the reverse would make a lot of sense.

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@mateuszz0000

mateuszz0000 May 14, 2020

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I am agreed. One question because this implementation needs recursive passing solution array because algorithm depends on deleting items from input source. Should I avoid recursion?

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@cclauss

cclauss May 14, 2020

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def strand_sort(arr: list, reverse: bool=False, solution: list=None):
    solution = solution or []
    your code goes here...

This will allow the caller to just pass in the arr to be sorted but also allows the function to call itself recursively. Best of both worlds.

strand_asc = partial(strand_sort, _operator=operator.gt)
strand_desc = partial(strand_sort, _operator=operator.lt)
Comment on lines 50 to 51

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@cclauss

cclauss May 14, 2020

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I'm not a fan. Let's lose partial and define strand_sort() to work like the Python builtin sorted() which has an optional reverse parameter that defaults to False.

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@mateuszz0000

mateuszz0000 May 14, 2020

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Sure! Just wondering: ispartial bad practice?

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@cclauss

cclauss May 14, 2020

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Partial has its place. I tend to use it rarely. The real point is that sort algorithms in Python should try to have similar calling conventions to the builtin sorted() so developers find them intuitive (Pythonic) to use.

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