perf(strings): optimize anagram signature using frequency counts (#12927)

* fix(strings): use frequency-based signature for anagrams

Replaced the sorting-based signature implementation with a frequency-based
approach using `collections.Counter`. This ensures that the signature
represents both characters and their counts, preventing collisions and
better grouping of true anagrams.

Examples:
- "test" → "e1s1t2"
- "finaltest" → "a1e1f1i1l1n1s1t2"
- "this is a test" → " 3a1e1h1i2s3t3"

Also updated the anagram lookup to use the new frequency-based signatures, making results more accurate and avoiding false positives.

* Refactor anagram function return type to list[str]

* Update anagrams.py

* Update anagrams.py

* Update anagrams.py

* Update anagrams.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: Maxim Smolskiy <mithridatus@mail.ru>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

strings/anagrams.py

@@ -6,19 +6,26 @@ from pathlib import Path
 
 
 def signature(word: str) -> str:
-    """Return a word sorted
-    >>> signature("test")
-    'estt'
-    >>> signature("this is a test")
-    '   aehiisssttt'
-    >>> signature("finaltest")
-    'aefilnstt'
     """
-    return "".join(sorted(word))
+    Return a word's frequency-based signature.
+
+    >>> signature("test")
+    'e1s1t2'
+    >>> signature("this is a test")
+    ' 3a1e1h1i2s3t3'
+    >>> signature("finaltest")
+    'a1e1f1i1l1n1s1t2'
+    """
+    frequencies = collections.Counter(word)
+    return "".join(
+        f"{char}{frequency}" for char, frequency in sorted(frequencies.items())
+    )
 
 
 def anagram(my_word: str) -> list[str]:
-    """Return every anagram of the given word
+    """
+    Return every anagram of the given word from the dictionary.
+
     >>> anagram('test')
     ['sett', 'stet', 'test']
     >>> anagram('this is a test')
@@ -40,5 +47,5 @@ if __name__ == "__main__":
     all_anagrams = {word: anagram(word) for word in word_list if len(anagram(word)) > 1}
 
     with open("anagrams.txt", "w") as file:
-        file.write("all_anagrams = \n ")
+        file.write("all_anagrams = \n")
         file.write(pprint.pformat(all_anagrams))