Given a string s
and an integer k
, return the length of the longest substring of s
such that the frequency of each character in this substring is greater than or equal to k
.
Example 1:
Input: s = "aaabb", k = 3
Output: 3
Explanation: The longest substring is "aaa", as 'a' is repeated 3 times.
Example 2:
Input: s = "ababbc", k = 2
Output: 5
Explanation: The longest substring is "ababb", as 'a' is repeated 2 times and 'b' is repeated 3 times.
Constraints:
-
1 <= s.length <= 104
-
s
consists of only lowercase English letters. -
1 <= k <= 105
SOLUTION:
class Solution:
def lstr(self, s, beg, end, k):
if end - beg < k:
return 0
ctr = [0] * 26
for i in range(beg, end):
ctr[ord(s[i]) - ord('a')] += 1
for i in range(beg, end):
if ctr[ord(s[i]) - ord('a')] < k:
return max(self.lstr(s, beg, i, k), self.lstr(s, i + 1, end, k))
return end - beg
def longestSubstring(self, s: str, k: int) -> int:
return self.lstr(s, 0, len(s), k)
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