Create first_missing_positive.py

[moaldeen]

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".

[cclauss]

>>> def x(nums):
...     return sorted(set(range(1, max(nums) + 2)) - set(nums))[0]
...
>>> x([2, 5, -10, 8, 4, 6, 1, 9])
3
>>> x([7, 8, 9, 11, 12])
1
>>> x([3, 4, -1, 1])
2
>>> x([1, 2, 0])
3

[cclauss]

Please add doctests for

>>> first_missing_positive([])
>>> first_missing_positive([0])
>>> first_missing_positive([1])
>>> first_missing_positive([1.1, 2.2, 3.3])
>>> first_missing_positive([-1, -2, -3])
>>> first_missing_positive("ABC")

[moaldeen]

thanks for the feedback .. i have done it

[cclauss]

Removing type hints is a bad idea.

[moaldeen]

hint was added

[moaldeen]

thanks for the feedback .. i have done it

[moaldeen]

fixed the hint

[moaldeen]

hint added

[moaldeen]

@cclauss i have made the adjustments, could you please review it. ? i really appreciate it.