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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int solve_for(char king, const string &s){
  5.     int n = s.size();
  6.     vector<int> pref(n+1, 0);
  7.  
  8.     for(int i = 1; i <= n; i++){
  9.         if(s[i-1] == king) pref[i] = pref[i-1] + 1;
  10.         else pref[i] = pref[i-1] - 1;
  11.     }
  12.  
  13.     stack<int> st;
  14.     for(int i = 0; i <= n; i++){
  15.         if(st.empty() || pref[i] < pref[st.top()])
  16.             st.push(i);
  17.     }
  18.  
  19.     int ans = 0;
  20.     for(int r = n; r >= 0; r--){
  21.         while(!st.empty() && pref[r] > pref[st.top()]){
  22.             ans = max(ans, r - st.top());
  23.             st.pop();
  24.         }
  25.     }
  26.     return ans;
  27. }
  28.  
  29. int main(){
  30.     ios::sync_with_stdio(false);
  31.     cin.tie(nullptr);
  32.  
  33.     int n;
  34.     cin >> n;
  35.     string s;
  36.     cin >> s;
  37.  
  38.     int ans = 0;
  39.     ans = max(ans, solve_for('a', s));
  40.     ans = max(ans, solve_for('b', s));
  41.     ans = max(ans, solve_for('c', s));
  42.  
  43.     cout << ans << '\n';
  44. }
  45.  
Success #stdin #stdout 0.01s 5296KB
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https://ideone.com/miGMDB
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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