0854. K-Similar Strings

https://leetcode.com/problems/k-similar-strings

Description

Strings s1 and s2 are k-similar (for some non-negative integer k) if we can swap the positions of two letters in s1 exactly k times so that the resulting string equals s2.

Given two anagrams s1 and s2, return the smallest k for which s1 and s2 are k-similar.

Example 1:

**Input:** s1 = "ab", s2 = "ba"
**Output:** 1

Example 2:

**Input:** s1 = "abc", s2 = "bca"
**Output:** 2

Example 3:

**Input:** s1 = "abac", s2 = "baca"
**Output:** 2

Example 4:

**Input:** s1 = "aabc", s2 = "abca"
**Output:** 2

Constraints:

• 1 <= s1.length <= 20

• s2.length == s1.length

• s1 and s2 contain only lowercase letters from the set {'a', 'b', 'c', 'd', 'e', 'f'}.

• s2 is an anagram of s1.

ac