import java.util.*;
import java.io.*;

public class VertexSet implements Iterable<Vertex> { 

    private ArrayList<Vertex> V;
    private Vertex[] vertex;

    public VertexSet (int n){
	V      = new ArrayList<Vertex>();
	vertex = new Vertex[n];
    }
    
    public VertexSet clone(){
	int n = 0;
	VertexSet S = new VertexSet(vertex.length);
	for (Vertex v : V) S.add((Vertex)v.clone());
	return S;
    }

    public void add(Vertex v){
	if (!V.contains(v)){
	    V.add(v);
	    vertex[v.getIndex()] = v;
	    v.setLocation(V.size()-1);
	}
    }

    /*
    private void delete(Vertex v){
	if (V.contains(v)){
	    V.remove(v);
	    vertex[v.getIndex()] = null;
	    for (Integer i : v) vertex[i].removeAdjacent(v);
	}
    }
    */

    private void delete(Vertex v){
	if (V.contains(v)){
	    int locn_v = v.getLocation();
	    Vertex w = V.get(V.size()-1);
	    V.set(locn_v,w);
	    w.setLocation(locn_v);
	    V.remove(V.size()-1);
	    vertex[v.getIndex()] = null;
	    for (Integer i : v) vertex[i].removeAdjacent(v);
	}
    }

    public int colour(Vertex v){	
	int col = v.colour();                     // get minimum colour for vertex v
	for (int j : v)                           // for adjacent vertices in P
	    if (vertex[j].hasColour(col)){        // does adjacent j have same colour available?
		vertex[j].removeColour(col);      // remove colour from domain of vertex j
		vertex[j].incrementSaturation();  // increase saturation of vertex j
	    }
	return col;
    }

    public void remove(int i){delete(vertex[i]);}
    public void remove(Vertex v){delete(vertex[v.getIndex()]);}
    public Vertex get(int i){return vertex[i];}
    public int size(){return V.size();}
    public boolean isEmpty(){return V.isEmpty();}
    public Iterator<Vertex> iterator(){return V.iterator();}

    public String toString(){
	return V.size() +" ";
    }
}