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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. bool ok(const vector<long long>& v, long long x) {
  5.     int m = v.size();
  6.     for (int i = 0; i < m; i++) {
  7.         for (int j = i + 1; j < m; j++) {
  8.             long long a = v[i], b = v[j];
  9.             // ba khả năng tạo CSC
  10.             if (a + b == 2 * x) return false;
  11.             if (a + x == 2 * b) return false;
  12.             if (b + x == 2 * a) return false;
  13.         }
  14.     }
  15.     return true;
  16. }
  17.  
  18. int main() {
  19.     ios::sync_with_stdio(false);
  20.     cin.tie(nullptr);
  21.  
  22.     int n;
  23.     cin >> n;
  24.     vector<long long> a(n);
  25.     for (int i = 0; i < n; i++) cin >> a[i];
  26.  
  27.     unordered_set<long long> st;
  28.     vector<long long> cur;
  29.  
  30.     int L = 0, best = 0, bestL = 0;
  31.  
  32.     for (int R = 0; R < n; R++) {
  33.         // đảm bảo không trùng
  34.         while (st.count(a[R])) {
  35.             st.erase(a[L]);
  36.             cur.erase(find(cur.begin(), cur.end(), a[L]));
  37.             L++;
  38.         }
  39.  
  40.         // đảm bảo không tạo CSC
  41.         while (!ok(cur, a[R])) {
  42.             st.erase(a[L]);
  43.             cur.erase(find(cur.begin(), cur.end(), a[L]));
  44.             L++;
  45.         }
  46.  
  47.         st.insert(a[R]);
  48.         cur.push_back(a[R]);
  49.  
  50.         if ((int)cur.size() > best) {
  51.             best = cur.size();
  52.             bestL = L;
  53.         }
  54.     }
  55.  
  56.     cout << best << "\n";
  57.     cout << bestL + 1 << " " << bestL + best << "\n";
  58.     return 0;
  59. }
Success #stdin #stdout 0.01s 5312KB
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https://ideone.com/MvgjVc
language:
C++ (gcc 8.3)
created:
2 days ago
visibility:
public

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