py_string_permutation_checker — Permutation / Anagram Check

Difficulty: hard

Write a function that determines if two strings are permutations of each other. Two strings are permutations if they contain the same characters with the same frequencies. The comparison is case-sensitive.

def string_permutation_checker(s1: str, s2: str) -> bool:

Examples

>>> string_permutation_checker("abc", "bca")
True

>>> string_permutation_checker("abc", "def")
False

>>> string_permutation_checker("listen", "silent")
True

>>> string_permutation_checker("hello", "bello")
False

>>> string_permutation_checker("", "")
True

>>> string_permutation_checker("a", "")
False

>>> string_permutation_checker("Abc", "abc")
False

>>> string_permutation_checker("a gentleman", "elegant man")
True

Solution

Download py_string_permutation_checker.py

def string_permutation_checker(s1: str, s2: str) -> bool:
    if len(s1) != len(s2):
        return False
    return sorted(s1) == sorted(s2)

How It Works

Goal: Confirm both strings use the same characters with the same multiplicities.

Approach: Two strings are permutations of each other iff their sorted character sequences are identical.

Step by step:

1. Length mismatch is an instant False (and an early exit avoids needless sorting).
2. sorted(s) returns a list of characters in ascending order.
3. Compare the two sorted lists with ==.

Key concept: Sorting normalizes any permutation to the same canonical form, so two permutations of the same multiset will always compare equal after sorting.