至少有K个重复字符的最长子串

Posted 2022-02-12 Alice_yufeng

class Solution 
    public int longestSubstring(String s, int k) 
        int ret = 0;
        int n = s.length();
        for (int t = 1; t <= 26; t++) 
            int l = 0, r = 0;
            int[] cnt = new int[26];
            int tot = 0;
            int less = 0;
            while (r < n) 
                cnt[s.charAt(r) - 'a']++;
                if (cnt[s.charAt(r) - 'a'] == 1) 
                    tot++;
                    less++;
                
                if (cnt[s.charAt(r) - 'a'] == k) 
                    less--;
                

                while (tot > t) 
                    cnt[s.charAt(l) - 'a']--;
                    if (cnt[s.charAt(l) - 'a'] == k - 1) 
                        less++;
                    
                    if (cnt[s.charAt(l) - 'a'] == 0) 
                        tot--;
                        less--;
                    
                    l++;
                
                if (less == 0) 
                    ret = Math.max(ret, r - l + 1);
                
                r++;
            
        
        return ret;