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fixed error in factorial.py #1888

Merged
merged 5 commits into from
Aug 5, 2020
Merged

fixed error in factorial.py #1888

merged 5 commits into from
Aug 5, 2020

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SandersLin
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@SandersLin SandersLin commented Apr 17, 2020 •
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Describe your change:

factorial(11) returns index out of range. To implement memoization an auxiliary function is required.

  • 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}.

wandrewp
wandrewp suggested changes May 13, 2020
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Recommend making factorial_aux a private function since no outside entity need use it.

Recommend putting the debug statements back in showing where to print result for debugging, although I noticed debugging it in that fashion causes docttest to print out a lot of example failed blocks.

Otherwise I think this change is good and it makes sense.

@TravisBuddy
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Hey @SandersLin,
Something went wrong with the build.

TravisCI finished with status errored, which means the build failed because of something unrelated to the tests, such as a problem with a dependency or the build process itself.

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TravisBuddy Request Identifier: 09604660-b535-11ea-aae7-0b05fcc524af

@ashishpawar517
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we can use math.factorial if required .

cclauss
cclauss reviewed Jul 8, 2020
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dynamic_programming/factorial.py Outdated
return factorial_aux(num, result)


def factorial_aux(num, result):
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Type hints? Doctests?

ashishpawar517
ashishpawar517 reviewed Jul 8, 2020
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Its working .!

fhlasek
fhlasek reviewed Aug 5, 2020
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dynamic_programming/factorial.py Outdated
result[num] = num * factorial(num - 1)
# uncomment the following to see how recalculations are avoided
# print(result)
result[num] = num * factorial_aux(num - 1, result)
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Technically, this is more of a "memoization" approach. While being perfectly correct, the more appropriate algorithm for this section may look as follows

Suggested change
result[num] = num * factorial_aux(num - 1, result)
result[0] = 1
for i in xrange(num):
result.append((i + 1) * result[i])
return result[num]

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xrange() was removed from Python on 1/1/2020.

The canonical way to do memoization in Python is with the lru_cache function decorator.

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Hey @SandersLin,
Something went wrong with the build.

TravisCI finished with status errored, which means the build failed because of something unrelated to the tests, such as a problem with a dependency or the build process itself.

View build log

TravisBuddy Request Identifier: aabb4010-d708-11ea-85fc-4b61cecd2c91

@cclauss cclauss merged commit f0d7879 into TheAlgorithms:master Aug 5, 2020
stokhos pushed a commit to stokhos/Python that referenced this pull request Jan 3, 2021
@SandersLin @l3str4nge
@cclauss @stokhos
fixed error in factorial.py (TheAlgorithms#1888)
d8c55b7 
* Update factorial.py

* updating DIRECTORY.md

* Update dynamic_programming/factorial.py

* Update factorial.py

Co-authored-by: mateuszz0000 <mtszzwdzk@gmail.com>
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>
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Reviewers

@fhlasek fhlasek fhlasek left review comments

@ashishpawar517 ashishpawar517 ashishpawar517 left review comments

@swapnanildutta swapnanildutta swapnanildutta approved these changes

@wandrewp wandrewp wandrewp requested changes

@cclauss cclauss cclauss approved these changes

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@SandersLin @TravisBuddy @ashishpawar517 @cclauss @fhlasek @wandrewp @swapnanildutta @l3str4nge