Description
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.
if no such substring exists, return 0.
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 <= 104sconsists of only lowercase English letters.1 <= k <= 105
Solution
Python3
class Solution:
def longestSubstring(self, st: str, k: int) -> int:
res = 0
stack = [st]
while stack:
s = stack.pop()
for c in set(s):
if s.count(c) < k:
stack.extend([ch for ch in s.split(c)])
break
else:
res = max(res, len(s))
return res