leetcode395 Longest Substring with At Least K Repeating Characters

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 class Solution 
 4 {
 5 public:
 6     int longestSubstring(string s, int k) 
 7     {
 8         int n = s.length();
 9         if (k == 1) return n;
10         int ans = 0;
11         vector<int> num(26, 0);
12         for (int i = 1; i <= 26; i++)
13         {
14             fill(num.begin(), num.end(), 0);
15             int slow = 0, fast = 0, cnt = 0;
16             set<char> st;
17             while (fast < n)
18             {
19                 while (fast < n)
20                 {
21                     if (num[s[fast] - ‘a‘] == 0) cnt++;
22                     num[s[fast] - ‘a‘]++;
23                     st.insert(s[fast]);
24                     fast++;
25                     if (cnt == i && fast < n && num[s[fast] - ‘a‘] == 0)
26                         break;
27                 }
28                 bool flg = true;
29                 for (auto it: st)
30                     if (num[it - ‘a‘] < k) { flg = false; break; }
31                 if (flg) ans = max(ans, fast - slow);
32                 if (fast == n) break;
33                 while (slow < fast && cnt == i)
34                 {
35                     num[s[slow] - ‘a‘]--;
36                     if (num[s[slow] - ‘a‘] == 0) { cnt--; st.erase(s[slow]); }
37                     slow++;
38                 }
39             }
40         }
41         return ans;
42     }
43 };
44 int main()
45 {
46     string s = "aabbccdcccde"; int k = 2;
47     cout << Solution().longestSubstring(s, k) << endl;
48     return 0;
49 }