395.-longest-substring-with-at-least-k-repeating-characters.md

395. Longest Substring with At Least K Repeating Characters

class Solution:
    def longestSubstring(self, s: str, k: int) -> int:
        
        
        ans = 0
        check = len(set(s))
        
        for i in range(1,check+1):
            left = right = 0
            window = collections.defaultdict(int)
            curr_ans = 0
            k_value = 0
            while right < len(s):
                window[s[right]] += 1
                if window[s[right]] == k:
                    k_value += 1
                right += 1
                while len(window) > i:
                    if window[s[left]] == k:
                        k_value -= 1
                    window[s[left]] -= 1
                    if window[s[left]] == 0:
                        del window[s[left]]
                    left += 1
                if k_value == i:
                    curr_ans = max(curr_ans,right - left)
            ans = max(curr_ans, ans)
            
        return ans