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 <= 20s2.length == s1.lengths1ands2contain only lowercase letters from the set{'a', 'b', 'c', 'd', 'e', 'f'}.s2is an anagram ofs1.