#ifndef _UNIONFIND_H
#define _UNIONFIND_H

#include <iostream>
#include <signal.h>

#include "Array.h"

// union/find data structure

// use like this:
//
//  #include "UnionFind.h"
// 
//  UnionFind a, b, c;
//  
//  a.merge(b);
//
//  if (a.find() == b.find()) ...
//  
//  be careful to 

class UnionFind {
  
 private:
  static int _n_components;

  UnionFind* parent;
  int _size;

  UnionFind(const UnionFind &a) {
    std::cerr << "UnionFind copy constructor called" << std::endl;
    exit(-1);
  }

 public:

  ~UnionFind() {}

  UnionFind() { _size = 1;  parent = this;  ++_n_components;}

  UnionFind * find() {
    UnionFind * root = this;
    while (root->parent != root) root = root->parent;

    // path compression
    UnionFind * p = this;
    while (p->parent != root) {
      UnionFind * pp = p->parent;
      p->parent = root;
      p = pp;
    }
    return root;
  }

  void merge(UnionFind& a) {
    UnionFind * r = find();
    UnionFind * ar = a.find();

    if (r != ar) {
      --_n_components;
      if (r->_size < ar->_size) {
	r->parent = ar;
	ar->_size += r->_size;
      }
      else {
	ar->parent = r;
	r->_size += ar->_size;
      }
    }
  }

  int size() const {
    return _size;
  }

  static int n_components() {
    return _n_components;
  }
};

int UnionFind::_n_components = 0;
#endif