<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_substr: List[str]) -> int:
        is_forbidden: Dict[str, bool] = defaultdict(bool)
        for forbidden_str in forbidden_substr:
            is_forbidden[forbidden_str] = True
        
        MAX_FORBIDDEN_LEN: int = 10
        first_wrong: int = len(word)
        longest_valid_substr: int = 0
        for char_idx, char in reversed(list(enumerate(word))):
            for forbidden_len in range(1, MAX_FORBIDDEN_LEN + 1):
                end_idx: int = char_idx + forbidden_len - 1
                if end_idx >= len(word):
                    break

                if is_forbidden[word[char_idx:(end_idx + 1)]]:
                    first_wrong = min(first_wrong, end_idx)
                    break
                
                if first_wrong <= end_idx:
                    break
                
                if forbidden_len == MAX_FORBIDDEN_LEN:
                    longest_valid_substr = max(
                        longest_valid_substr,
                        first_wrong - char_idx
                    )
                else:
                    longest_valid_substr = max(
                        longest_valid_substr,
                        forbidden_len
                    )
               # print(char_idx, first_wrong, forbidden_len, first_wrong - char_idx)
        
        return longest_valid_substr

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