IsAnagram bug (per element counts)

[ZacharyPatten]

Describe the bug

The IsAnagram function is not checking per-element counts. It is only checking if they have the same elements, but not if the count of each element matches.

A more appropriate name for the current logic is something like ContainsNoDifferingElements or IntersectsMatch rather than IsAnagram. I would recommend changing the name or the logic of the method.

Note: If you aren't going to check per-element counts, then you should also get rid of this check in IsAnagrams:

if (source.Length != other.Length)
    return false;

because length doesn't matter if you don't also check per-element counts.

To Reproduce

Add the following case to the IsAnagram unit tests:

string aab = "aab";
string abb = "abb";
Assert.False(Permutations.IsAnargram(aab, abb));

Expected behavior

Spans of the same length and elements but different per-element counts should not be considered re-orders/anagrams of each other.

Environment:

master branch

Additional context

I have written my own version of this algorithm in C# (that fixes this issue) if interested here...

Source Code: https://github.com/ZacharyPatten/Towel/blob/d2660e208ad3a44ab22f192834760c5b93dc82ac/Sources/Towel/Statics-SequenceAnalysis.cs#L1321
Examples: https://github.com/ZacharyPatten/Towel/blob/d2660e208ad3a44ab22f192834760c5b93dc82ac/Examples/BasicsAndExtensions/Program.cs#L406
Testing: https://github.com/ZacharyPatten/Towel/blob/d2660e208ad3a44ab22f192834760c5b93dc82ac/Tools/Towel_Testing/Statics.cs#L2086
Note: MapHashLinked is my version of a Dictionary if you look at the source code.

[ZacharyPatten]

related to #11

[github-actions]

Thanks for supporting the development of C# Algorithms with your first issue! We look forward to handling it.