Updated maths/number_of_digits.py

[vasugamdha]

Added two more methods!

Fixes: #2220
I have added 2 methods for maths/number_of_digits.py:

1. num_digits2(): Also an O(n) algorithm approach.
2. num_digits_fast(): An O(1) algorithm for counting the number of digits

• 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}.

closes #2220

[TravisBuddy]

Hey @vasugamdha,
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[vasugamdha]

@cclauss I don't know why my PR is failing TravisCI checks. Please suggest some changes that need to be implemented to pass the checks. @TravisBuddy

[cclauss]

https://github.com/TheAlgorithms/Python/blob/master/Travis_CI_tests_are_failing.md

[TravisBuddy]

Hey @vasugamdha,
Something went wrong with the build.

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[vasugamdha]

@cclauss I have fixed the #2220 issue and it's ready for review and merge.

[vasugamdha]

hello @cclauss , can you please merge this PR, as it has already passed both the checks and fixes the #2220 issue? Thanks.

[cclauss]

Unfortunately, I see no benchmark code.

[vasugamdha]

I haven't written benchmark code, as the function , I defined (num_digits_fast()), clearly returns number of digits in O(1). While the one already written function returns the same in O(n).

[cclauss]

What proof do you have for those theoretical statements without benchmarking them with the same data?
Here examples of algorithms with benchmarks using timeit: https://github.com/TheAlgorithms/Python/search?q=timeit

[TravisBuddy]

Hey @vasugamdha,
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[TravisBuddy]

Hey @vasugamdha,
Something went wrong with the build.

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[TravisBuddy]

Travis tests have failed

Hey @vasugamdha,
Please read the following log in order to understand the failure reason.
It'll be awesome if you fix what's wrong and commit the changes.

TravisBuddy Request Identifier: bcddb020-cf06-11ea-9502-ed86ad10d0d8

[vasugamdha]

First comment update!!

Added two more methods!

Fixes: #2220
I have added 2 methods for maths/number_of_digits.py, which are comparatively faster then already present method:

1. num_digits_fast()
2. num_digits_faster()

Here is the output of the benchmark code.

[vasugamdha]

@cclauss Please review it now!

[TravisBuddy]

Hey @vasugamdha,
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[cclauss]

Impressive!!!