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  1. #include <bits/stdc++.h>
  2. #define ll long long
  3. #define in cin
  4. #define out cout
  5. #define endl '\n'
  6. using namespace std;
  7.  
  8. bool isPrime(int n) {
  9.     if (n <= 1) return false;
  10.     for (int i = 2; i * i <= n; i++)
  11.         if (n % i == 0) return false;
  12.     return true;
  13. }
  14.  
  15. bool primes[100];
  16. vector<ll> ring;
  17. vector<bool> used(20);
  18.  
  19. void rec(ll n, ll index) {
  20.     if (index == n) {
  21.         if (primes[ring[n-1] + ring[0]]) {
  22.             for (int i = 0; i < n; i++) out << ring[i] << ' ';
  23.             out << endl;
  24.         }
  25.         return;
  26.     }
  27.  
  28.     for (int i = 2; i <= n; i++) {
  29.         if (!used[i] && primes[ ring[index - 1] + i ]) {
  30.             ring[index] = i;
  31.             used[i] = true;
  32.             rec(n, index + 1);
  33.             used[i] = false;
  34.         }
  35.     }
  36. }
  37.  
  38. int main() {
  39.     ios_base::sync_with_stdio(false);
  40.     cin.tie(NULL);
  41.  
  42.     for (int i = 1; i < 100; i++) primes[i] = isPrime(i);
  43.  
  44.     ll n, cases = 1;
  45.     while (in >> n) {
  46.         if (cases > 1) out << endl;
  47.         out << "Case " << cases++ << ":" << endl;
  48.         ring.assign(n, 0);
  49.         fill(used.begin(), used.end(), false);
  50.         ring[0] = 1;
  51.         used[1] = true;
  52.         rec(n, 1);
  53.     }
  54. }
  55.  
Success #stdin #stdout 0.01s 5316KB
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https://ideone.com/RoSk7d
language:
C++ (gcc 8.3)
created:
3 days ago
visibility:
public

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