<p>You are given a string <code>word</code> and an array of strings <code>forbidden</code>.</p>

<p>A string is called <strong>valid</strong> if none of its substrings are present in <code>forbidden</code>.</p>

<p>Return <em>the length of the <strong>longest valid substring</strong> of the string </em><code>word</code>.</p>

<p>A <strong>substring</strong> is a contiguous sequence of characters in a string, possibly empty.</p>

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

<pre>
<strong>Input:</strong> word = &quot;cbaaaabc&quot;, forbidden = [&quot;aaa&quot;,&quot;cb&quot;]
<strong>Output:</strong> 4
<strong>Explanation:</strong> There are 11 valid substrings in word: &quot;c&quot;, &quot;b&quot;, &quot;a&quot;, &quot;ba&quot;, &quot;aa&quot;, &quot;bc&quot;, &quot;baa&quot;, &quot;aab&quot;, &quot;ab&quot;, &quot;abc&quot; and &quot;aabc&quot;. The length of the longest valid substring is 4. 
It can be shown that all other substrings contain either &quot;aaa&quot; or &quot;cb&quot; as a substring. </pre>

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

<pre>
<strong>Input:</strong> word = &quot;leetcode&quot;, forbidden = [&quot;de&quot;,&quot;le&quot;,&quot;e&quot;]
<strong>Output:</strong> 4
<strong>Explanation:</strong> There are 11 valid substrings in word: &quot;l&quot;, &quot;t&quot;, &quot;c&quot;, &quot;o&quot;, &quot;d&quot;, &quot;tc&quot;, &quot;co&quot;, &quot;od&quot;, &quot;tco&quot;, &quot;cod&quot;, and &quot;tcod&quot;. The length of the longest valid substring is 4.
It can be shown that all other substrings contain either &quot;de&quot;, &quot;le&quot;, or &quot;e&quot; as a substring. 
</pre>

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

<ul>
	<li><code>1 &lt;= word.length &lt;= 10<sup>5</sup></code></li>
	<li><code>word</code> consists only of lowercase English letters.</li>
	<li><code>1 &lt;= forbidden.length &lt;= 10<sup>5</sup></code></li>
	<li><code>1 &lt;= forbidden[i].length &lt;= 10</code></li>
	<li><code>forbidden[i]</code> consists only of lowercase English letters.</li>
</ul>

class Solution:
    def longestValidSubstring(self, word: str, forbidden: List[str]) -> int:

        prefix_tree = {}
        
        for w in forbidden:
            pointer = prefix_tree
            for char in w[::-1]:
                if not char in pointer:
                    
                    pointer[char] = {}
                
                pointer = pointer[char]
            pointer["end"] = True
        
        start = 0

        max_len = 0

        print(word)
        print(prefix_tree)

        # sliding window
        l = 0
        for r in range(len(word)):

            # match with prefix tree
            idx = r
            #print("Checking for ", word[r])
            # O(10)
            pointer = prefix_tree
            while idx >= l and word[idx] in pointer:
                pointer = pointer[word[idx]]
                if "end" in pointer:
                    l = idx + 1
                    #print(f"matched {word[idx:r+1]}")
                    break
                idx -= 1
            
            max_len = max(max_len, r-l+1)
        
        return max_len
            



        
        '''
        for idx, char in enumerate(word):
            
            pointer = prefix_tree
            cp = idx
            print(f"checking match from {idx}: {char}")
            # O(10)
            while cp < len(word) and word[cp] in pointer:
                print(f"Matched {word[cp]}")
                pointer = pointer[word[cp]]
                if "end" in pointer:
                    print(f"match found from {idx}:{cp}, {word[idx:cp+1]}")
                    start = cp + 1
                
                cp += 1
            
            max_len = max(max_len, idx-start+1)
        '''

        #return max_len
1518