add algorithm to check if given string is valid number or not

[reniz-shah]

Add a new file string_is_valid_number.py in string directory

Describe your change:

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• 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".

[reniz-shah]

Need to migrate to NumPy 2.0 as ruff tests are failing or need to change test configurations

Below is the error raised by ruff check
graphs/multi_heuristic_astar.py:82:12: NPY201 np.chararray will be removed in NumPy 2.0. Use numpy.char.chararray instead.

[algorithms-keeper]

Click here to look at the relevant links ⬇️

🔗 Relevant Links

Repository:

• Contributing guidelines
• Project Euler solution guidelines

Python:

• Formatted string literals (f-strings)
• Type hints
• doctest
• unittest
• pytest

Automated review generated by algorithms-keeper. If there's any problem regarding this review, please open an issue about it.

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[algorithms-keeper]

Click here to look at the relevant links ⬇️

🔗 Relevant Links

Repository:

• Contributing guidelines
• Project Euler solution guidelines

Python:

• Formatted string literals (f-strings)
• Type hints
• doctest
• unittest
• pytest

Automated review generated by algorithms-keeper. If there's any problem regarding this review, please open an issue about it.

---

algorithms-keeper commands and options

algorithms-keeper actions can be triggered by commenting on this PR:

• @algorithms-keeper review to trigger the checks for only added pull request files
• @algorithms-keeper review-all to trigger the checks for all the pull request files, including the modified files. As we cannot post review comments on lines not part of the diff, this command will post all the messages in one comment.

NOTE: Commands are in beta and so this feature is restricted only to a member or owner of the organization.

[cclauss]

Please rebase this pull request on the current master branch.

[priya-sundaram-dev]

Reviewed in the oldest-PR triage sweep. Nice work — a DFA-based validator is a genuinely instructive addition, and it's close to merge-ready.

• Good use of Enum for CharType/State, a clear transition table, full type hints, and thorough doctests.

Two small nits before merge:

• The Solution By: Reniz Shah line in the module docstring — our convention is to keep author names out of the source (git already records authorship). Please drop it.
• Please rebase onto master so the current ruff/ty checks run.

Content-wise I'm happy with it. Thanks!