Added solution to Project Euler 69

[sarthaka1310]

Describe your change:

For #hacktoberfest
Added solution to Project Euler 69 for issue #2695

• 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}.

[sarthaka1310]

@dhruvmanila Implemented the requested changes, please review.
If found acceptable, please add the hacktoberfest-accepted label.

[dhruvmanila]

Suggested change

	raise ValueError("Please enter a natural number")
	raise ValueError("Please enter a natural number greater than 0")

[sarthaka1310]

Natural numbers are greater than 0 by definition. If you still want it, I'll commit :)

[dhruvmanila]

Yes, please, or maybe write something like the input value must be greater than 0 and please put the if statement back as that was a mistake on my part. Did you not realize that your code would become incorrect without the if statement?

[dhruvmanila]

Suggested change

	for number in range(2, n + 1):
	if phi[number] == number:
	phi[number] -= 1
	for multiple in range(number * 2, n + 1, number):
	phi[multiple] = (phi[multiple] // number) * (number - 1)
	for number in range(2, n + 1):
	phi[number] -= 1
	for multiple in range(number * 2, n + 1, number):
	phi[multiple] = (phi[multiple] // number) * (number - 1)

[dhruvmanila]

That line always evaluates to True so it's not needed.

[sarthaka1310]

After I accepted this, the test failed. Are you sure of this?

[dhruvmanila]

This was a mistake on my part. I did not see that you were changing the later elements of the list in the nested for loop. Please change it back.

[dhruvmanila]

I'm curious as to how did you not realize that your code would become incorrect without the if statement?

[sarthaka1310]

I did know what happened but gave you the benefit of doubt. Here's an explanation of what went wrong:
With the edit you made, the loop did not identify primes anymore and executed this for all numbers instead, therefore affecting the ratio.

[sarthaka1310]

@dhruvmanila I have another open PR#2868 and would appreciate it if you could review that too. (Also, it uses the sieve creation similar to the phi constructed here)

[dhruvmanila]

As mentioned, only submit one PR at a time. I have a lot to go through so that might take days. Thank you for your cooperation.

[TravisBuddy]

Travis tests have failed

Hey @sarthaka1310,
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: e9a2f7c0-0be5-11eb-a59b-f3f3774a9991