<p>Given a string <code>s</code> and an integer <code>k</code>, return <em>the length of the longest substring of</em> <code>s</code> <em>such that the frequency of each character in this substring is greater than or equal to</em> <code>k</code>.</p>

<p data-pm-slice="1 1 []">if no such substring exists, return 0.</p>

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

<pre>
<strong>Input:</strong> s = &quot;aaabb&quot;, k = 3
<strong>Output:</strong> 3
<strong>Explanation:</strong> The longest substring is &quot;aaa&quot;, as &#39;a&#39; is repeated 3 times.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;ababbc&quot;, k = 2
<strong>Output:</strong> 5
<strong>Explanation:</strong> The longest substring is &quot;ababb&quot;, as &#39;a&#39; is repeated 2 times and &#39;b&#39; is repeated 3 times.
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 10<sup>4</sup></code></li>
	<li><code>s</code> consists of only lowercase English letters.</li>
	<li><code>1 &lt;= k &lt;= 10<sup>5</sup></code></li>
</ul>

class Solution:
    def longestSubstring(self, s: str, k: int) -> int:
        
        pre = [[0 for _ in range(26)] for _ in range(len(s))]
        for i in range(len(s)):
            v = ord(s[i]) - 97
            pre[i][v] += 1
        for i in range(1 , len(s)):
            for j in range(26):
                pre[i][j] += pre[i-1][j]
        
        def get(j, l , r):
            if not l:
                return pre[r][j]
            return pre[r][j] - pre[l-1][j]
        
        def solve(i , j):
            if i > j or i < 0:
                return 0
            mi = float("inf")
            for l in range(i , j+1):
                v = ord(s[l]) - 97
                mi = min(mi , get(v , i , j))            
            
            if mi >= k:
                return j - i + 1
            
            ans = 0
            ii , jj = i , i
            while jj <= j:
                v = ord(s[jj]) - 97
                if get(v , i , j) < k:
                    ans = max(ans , solve(ii , jj-1))
                    jj += 1
                    ii = jj
                else:
                    jj += 1
            
            ans = max(ans , solve(ii , jj-1))
            return ans

        return solve(0, len(s) - 1)
        
21738