Changed knuth_morris_pratt to be consistent with str.find()

[Akashram28]

Describe your change:

function kmp() now returns the first occurrence of the pattern. If the pattern does not exist in the given text, it returns -1

See #9077

• 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 Returning index instead of boolean when knuth_morris_pratt matches. #9077".

[rohan472000]

Change bool return type to int for kmp function.

[rohan472000]

In your PR description, you should tick whatever suits your PR but don't delete other checkboxes, also tick that checkbox for bug fixing or doc change which u deleted.

[rohan472000]

@cclauss , kindly review it.

[amirsoroush]

Thanks. "doctests" are more desirable than print statements. While we're at it, let's write some tests instead.

[amirsoroush]

Just to note, you can use some keywords in your commit message to link a pull request to an issue, that way if your PR is accepted, the linked issue gets closed automatically. https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue

[rohan472000]

LGTM

[cclauss]

I added doctests that fail...

=================================== FAILURES ===================================
___________ [doctest] strings.knuth_morris_pratt.knuth_morris_pratt ____________
009     1) Preprocess pattern to identify any suffixes that are identical to prefixes
010 
011         This tells us where to continue from if we get a mismatch between a character
012         in our pattern and the text.
013 
014     2) Step through the text one character at a time and compare it to a character in
015         the pattern updating our location within the pattern if necessary
016 
017     >>> kmp = "knuth_morris_pratt"
018     >>> knuth_morris_pratt(kmp, "kn") == kmp.find("kn")
Expected:
    True
Got:
    False

As discussed in CONTRIBUTING.md, you can run these on your own computer with:
python3 -m doctest -v strings/knuth_morris_pratt.py

[rohan472000]

while testing the doctests added by @cclauss with existing code of knuth_morris_pratt.py in repo, it is also failing.

[Akashram28]

The pattern is the first parameter, the text is the second. Or am I doing something wrong ? Sry this is my first PR

[cclauss]

If we are going to be consistent with str.find() then we should change knuth_morris_pratt(sub, text) to knuth_morris_pratt(text, sub) to match the str.find() calling conventions and knuth_morris_pratt(text, sub) == text.find(sub) should always be True.