<p>Given the strings <code>s1</code> and <code>s2</code> of size <code>n</code> and the string <code>evil</code>, return <em>the number of <strong>good</strong> strings</em>.</p>

<p>A <strong>good</strong> string has size <code>n</code>, it is alphabetically greater than or equal to <code>s1</code>, it is alphabetically smaller than or equal to <code>s2</code>, and it does not contain the string <code>evil</code> as a substring. Since the answer can be a huge number, return this <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> n = 2, s1 = &quot;aa&quot;, s2 = &quot;da&quot;, evil = &quot;b&quot;
<strong>Output:</strong> 51 
<strong>Explanation:</strong> There are 25 good strings starting with &#39;a&#39;: &quot;aa&quot;,&quot;ac&quot;,&quot;ad&quot;,...,&quot;az&quot;. Then there are 25 good strings starting with &#39;c&#39;: &quot;ca&quot;,&quot;cc&quot;,&quot;cd&quot;,...,&quot;cz&quot; and finally there is one good string starting with &#39;d&#39;: &quot;da&quot;.&nbsp;
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> n = 8, s1 = &quot;leetcode&quot;, s2 = &quot;leetgoes&quot;, evil = &quot;leet&quot;
<strong>Output:</strong> 0 
<strong>Explanation:</strong> All strings greater than or equal to s1 and smaller than or equal to s2 start with the prefix &quot;leet&quot;, therefore, there is not any good string.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> n = 2, s1 = &quot;gx&quot;, s2 = &quot;gz&quot;, evil = &quot;x&quot;
<strong>Output:</strong> 2
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>s1.length == n</code></li>
	<li><code>s2.length == n</code></li>
	<li><code>s1 &lt;= s2</code></li>
	<li><code>1 &lt;= n &lt;= 500</code></li>
	<li><code>1 &lt;= evil.length &lt;= 50</code></li>
	<li>All strings consist of lowercase English letters.</li>
</ul>

class Solution:
    def __init__(self):
        self.convert = {char: num for char,num in zip("abcdefghijklmnopqrstuvwxyz", range(26))}
        self.MOD = 10**9 + 7
    def is_suffix(self,A, B):
        if len(B) > len(A):
            return False
        return A[-len(B):] == B
    def get(self, i, left, right, mistake):
        if mistake == len(self.evil):
            return 0 
        if i == self.n:
            return 1

        con = i, left, right, mistake
        if self.dp.get(con) is not None:
            return self.dp[con]

        res = 0
        start, end = 0, 25
        if left:
            start = self.s1[i]
        if right:
            end = self.s2[i]

        for x in range(start, end + 1):
            next_left = left and (x == self.s1[i])
            next_right = right and (x == self.s2[i])
            next_mistake = mistake
            #print(mistake)
            if(x==self.evil[mistake]):
                res=(res+self.get(i+1,next_left,next_right,mistake+1))%self.MOD
            else:
                temp=0
                for j in range(mistake):
                    if(x==self.evil[j]):
                        A=self.evil[:mistake]+[x]
                        B=self.evil[:j+1]
                        if(self.is_suffix(A,B)):
                            temp=j+1
                #print(i,x,temp)
                res=(res+self.get(i+1,next_left,next_right,temp))%self.MOD
        self.dp[con] = res
        return res

    def findGoodStrings(self, n: int, s1: str, s2: str, evil: str) -> int:
        self.s1 = [self.convert[x] for x in s1]
        self.s2 = [self.convert[x] for x in s2]
        self.evil = [self.convert[x] for x in evil]
        self.n = n
        self.dp = dict()
        return self.get(0, True, True, 0)
19300