Create cyclic_sort.py

[sharansukesh1003]

Describe your change:

• 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 include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

[cclauss]

 027     >>> cyclic_sort([-2, -5, -45])
UNEXPECTED EXCEPTION: IndexError('list index out of range')
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.11.5/x64/lib/python3.11/doctest.py", line 1351, in __run
    exec(compile(example.source, filename, "single",
  File "<doctest sorts.cyclic_sort.cyclic_sort[2]>", line 1, in <module>
  File "/home/runner/work/Python/Python/sorts/cyclic_sort.py", line 39, in cyclic_sort
    if nums[i] != nums[correct_index]:
                  ~~~~^^^^^^^^^^^^^^^
IndexError: list index out of range
/home/runner/work/Python/Python/sorts/cyclic_sort.py:27: UnexpectedException

[tianyizheng02]

1. The code is taken directly from the Stackademic article you reference in Feature: Cyclic Sort #9251: https://blog.stackademic.com/coding-pattern-cyclic-sort-96511b0f60ac
2. Like you said in Feature: Cyclic Sort #9251, one reason why cyclic sort is a distinct algorithm from cycle sort is that

Cyclic sort assumes that the elements to be sorted are integers in a specific range.

The algorithm you propose basically only works if the list elements are within the range 1 to n. Naturally, cyclic_sort([-2, -5, -45]) would then fail since you're indexing out of bounds of the array. Why add this as a unit test when you're aware of this difference?

[sharansukesh1003]

Made the changes.

…

On Sun, Oct 1, 2023 at 9:58 PM Tianyi Zheng ***@***.***> wrote: 1. The code is taken directly from the Stackademic article you reference in #9251 <#9251>: https://blog.stackademic.com/coding-pattern-cyclic-sort-96511b0f60ac 2. Like you said in #9251 <#9251>, one reason why cyclic sort is a distinct algorithm from cycle sort is that Cyclic sort assumes that the elements to be sorted are integers in a specific range. The algorithm you propose basically only works if the list elements are within the range 1 to n. Naturally, cyclic_sort([-2, -5, -45]) would then fail since you're indexing out of bounds of the array. Why add this as a unit test when you're aware of this difference? — Reply to this email directly, view it on GitHub <#9256 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ASOEZSDPGVMWECMWXYK7YYTX5GKZHANCNFSM6AAAAAA5OGWOBA> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[sharansukesh1003]

Hey can any of the admins review this, all tests have been passed.

[jeffreyyancey]

This algorithm looks correct and nearly ready to be approved.

I'd just ask that you add input constraints and add those cases to your doctests.

[jeffreyyancey]

I'd recommend adding the input constraints.

This algorithm only works correctly when the elements range from 1 to n with no duplicates. Stating this constraint on the inputs to any potential users of the algorithm can help prevent confusion should they provide a list of integers that does not fit the criteria and end up in an infinite loop or some other unexpected behaviour.

[jeffreyyancey]

Similar to above, I'd recommend adding an example to demonstrate what happens if the list contains elements outside the expected range (a non-positive integer) or duplicates are present in the list. This would show why this algorithm should not be used for those sets of values.

[jeffreyyancey]

This would be a good place to ensure the inputs meet the constraints of the algorithm. If they don't, indicate to the user what the issue is with the provided list.

[jeffreyyancey]

The algorithm is specified to sort integers, so a more correct typehint would be list[int] for the nums and the method output.