binomial.hh

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#ifndef __MINLCA_UTILS_GENERATORS_BINOMIAL_HH
#define __MINLCA_UTILS_GENERATORS_BINOMIAL_HH

#include <lemon/smart_graph.h>
#include <lemon/random.h>
#include <utils/generators/random-graph.hh>
#include <algorithm>


namespace minlca
{
namespace utils
{

template<typename BaseGraph = lemon::SmartGraph>
class BinomialRandom : public RandomGraph<BaseGraph>
{
protected:
  typedef BinomialRandom<BaseGraph> Graph;
  typedef RandomGraph<BaseGraph> Base;

public:
  TEMPLATE_GRAPH_TYPEDEFS(Graph);

protected:
  using Base::_r;
  int _n; 
  double _p; 

public:
  template<typename Number = int>
  BinomialRandom(Number seed = 0)
    : Base(seed)
  {
  }

  BinomialRandom(lemon::Random &r)
    : Base(r)
  {
  }

  Graph &init(
    int n, 
    double p 
  )
  {
    _n = n;
    _p = std::max(0.0, std::min(p, 1.0));;

    return *this;
  }

  double p() const
  {
    return _p;
  }

  virtual void generate()
  {
    this->clear();
    this->reserveNode(_n);
    this->reserveEdge(static_cast<int>(0.5 * _p * _n * (_n - 1)));

    for (int u = 0; u < _n; ++u) {
      this->addNode();
    }

    for (int u = 0; u < _n; ++u)
      for (int v = u + 1; v < _n; ++v)
        if (_r->boolean(_p)) {
          this->addEdge(this->nodeFromId(u), this->nodeFromId(v));
        }
  }
};
}
}

#endif