#include <iostream>
#include <cstdlib>

using std::cout;
using std::ostream;

template <class T>
class Sampler {
  T * buf;
  int s;
  int current;
  
 public:
  Sampler() {
    s=50;
    current=0;
    buf=new T[s];
  }

  Sampler(int n) {
    s=n;
    current=0;
    buf=new T[s];
  }

 private:
  Sampler(const Sampler&);
  Sampler & operator=(const Sampler&);

 public:
  T& operator[](int i) {
    return buf[i];
  }

  const T& operator[](int i)const {
    return buf[i];
  }

  int size()const {
    if (current<=s)
      return current;
    else 
      return s;
  }

  int maxSize()const {
    return s;
  }

  bool get(const T& t) {
    current++;
    if (current<=s) {
      buf[current-1]=t;
      return true;
    }  
    float r=(float)rand()/RAND_MAX;
    if (r<(float)s/current) {  //with probability s/current
      int r=rand()%s;          //choose a spot uniformly and replace
      for (int i=r; i<s-1; i++) 
	buf[i]=buf[i+1];
      buf[s-1]=t;
      return true;
    }
    return false;
  }

  ~Sampler() {
    delete[] buf;
  }
};

template <class T>
ostream& operator<<(ostream& os, const Sampler<T>& sampler) {
  for (int i=0; i<sampler.size(); i++) 
    cout<<sampler[i]<<" ";
  return os;
}