044: Steiner triple systems

/*
  
  Steiner triplets (using sets) in Comet.
 
  This Comet model was created by Hakan Kjellerstrand (hakank@gmail.com)
  Also, see my Comet page: http://www.hakank.org/comet 

 */

// Licenced under CC-BY-4.0 : http://creativecommons.org/licenses/by/4.0/

import cotfd;
int t0 = System.getCPUTime();

Solver<CP> cp();

int n = 9;
int nb = n *(n-1) / 6;
cout << "nb: " << nb << endl;

int c = 3; // cardinality
var<CP>{set{int}} steiner[1..nb](cp, 1..n, c);

Integer num_solutions(0);

exploreall<cp>{
  forall(i in 1..nb, j in 1..nb : i < j) {
    cp.post(atmostIntersection(steiner[i], steiner[j], 1));
  }
} using {

  // label(cp);
  forall(i in 1..nb)
    label(steiner[i]);

  cout << steiner << endl;

  num_solutions := num_solutions + 1;

}


cout << "\nnum_solutions: " << num_solutions << endl;
    
int t1 = System.getCPUTime();
cout << "time:      " << (t1-t0) << endl;
cout << "#choices = " << cp.getNChoice() << endl;
cout << "#fail    = " << cp.getNFail() << endl;
cout << "#propag  = " << cp.getNPropag() << endl;