public class Solution
extends Object
1397 - Find All Good Strings\.
Hard
Given the strings `s1` and `s2` of size `n` and the string `evil`, return _the number of **good** strings_.
A **good** string has size `n`, it is alphabetically greater than or equal to `s1`, it is alphabetically smaller than or equal to `s2`, and it does not contain the string `evil` as a substring. Since the answer can be a huge number, return this **modulo** 109 + 7.
**Example 1:**
**Input:** n = 2, s1 = "aa", s2 = "da", evil = "b"
**Output:** 51
**Explanation:** There are 25 good strings starting with 'a': "aa","ac","ad",...,"az". Then there are 25 good strings starting with 'c': "ca","cc","cd",...,"cz" and finally there is one good string starting with 'd': "da".
**Example 2:**
**Input:** n = 8, s1 = "leetcode", s2 = "leetgoes", evil = "leet"
**Output:** 0
**Explanation:** All strings greater than or equal to s1 and smaller than or equal to s2 start with the prefix "leet", therefore, there is not any good string.
**Example 3:**
**Input:** n = 2, s1 = "gx", s2 = "gz", evil = "x"
**Output:** 2
**Constraints:**
* `s1.length == n`
* `s2.length == n`
* `s1 <= s2`
* `1 <= n <= 500`
* `1 <= evil.length <= 50`
* All strings consist of lowercase English letters.