1363F Rotating Substrings
问题描述
You are given two strings s and t, each of length n and consisting of lowercase Latin alphabets. You want to make s equal to t.
You can perform the following operation on s any number of times to achieve it —
Choose any substring of s and rotate it clockwise once, that is, if the selected substring is s[l,l+1…r], then it becomes s[r,l,l+1…r−1]. All the remaining characters of s stay in their position.
For example, on rotating the substring [2,4] , string “abcde” becomes “adbce”.
A string a is a substring of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters from the beginning and several (possibly, zero or all) characters from the end.
Find the minimum number of operations required to convert s to t, or determine that it’s impossible.
Input
The first line of the input contains a single integer t (1≤t≤2000) — the number of test cases. The description of the test cases follows.
The first line of each test case contains a single integer n (1≤n≤2000) — the length of the strings.
The second and the third lines contain strings s and t respectively.
The sum of n over all the test cases does not exceed 2000.
Output
For each test case, output the minimum number of operations to convert s to t. If it is not possible to convert s to t, output −1 instead.