/**
 * A class representing a Graph
 *
 * @author Mark Allen Weiss with modifications by Greg Gagne
 */

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

public class Graph
{
    public static final int INFINITY = Integer.MAX_VALUE;
    private HashMap vertexMap = new HashMap( );    // Maps vertices to internal Vertex

    /**
     * Add the edge connecting the vertices sourceName and destName
     * to the graph.
     */
    public void addEdge( String sourceName, String destName )
    {
        Vertex v = getVertex( sourceName );
        Vertex w = getVertex( destName );
        v.adj.add( w );
    }

      // If vertexName is not present, add it to vertexMap.
      // In either case, return the Vertex.
    public Vertex getVertex( String vertexName )
    {
        Vertex v = (Vertex) vertexMap.get( vertexName );
        if( v == null )
        {
            v = new Vertex( vertexName );
            vertexMap.put( vertexName, v );
        }
        return v;
    }
}