DegreesOfSeparation.java

Below is the syntax highlighted version of DegreesOfSeparation.java from §4.1 Undirected Graphs.

/******************************************************************************
 *  Compilation:  javac DegreesOfSeparation.java
 *  Execution:    java DegreesOfSeparation filename delimiter source
 *  Dependencies: SymbolGraph.java Graph.java BreadthFirstPaths.java StdOut.java
 *  Data files:   https://algs4.cs.princeton.edu/41graph/routes.txt
 *                https://algs4.cs.princeton.edu/41graph/movies.txt
 *
 *
 *  %  java DegreesOfSeparation routes.txt " " "JFK"
 *  LAS
 *     JFK
 *     ORD
 *     DEN
 *     LAS
 *  DFW
 *     JFK
 *     ORD
 *     DFW
 *  EWR
 *     Not in database.
 *
 *  % java DegreesOfSeparation movies.txt "/" "Bacon, Kevin"
 *  Kidman, Nicole
 *     Bacon, Kevin
 *     Woodsman, The (2004)
 *     Grier, David Alan
 *     Bewitched (2005)
 *     Kidman, Nicole
 *  Grant, Cary
 *     Bacon, Kevin
 *     Planes, Trains & Automobiles (1987)
 *     Martin, Steve (I)
 *     Dead Men Don't Wear Plaid (1982)
 *     Grant, Cary
 *
 *  % java DegreesOfSeparation movies.txt "/" "Animal House (1978)"
 *  Titanic (1997)
 *     Animal House (1978)
 *     Allen, Karen (I)
 *     Raiders of the Lost Ark (1981)
 *     Taylor, Rocky (I)
 *     Titanic (1997)
 *  To Catch a Thief (1955)
 *     Animal House (1978)
 *     Vernon, John (I)
 *     Topaz (1969)
 *     Hitchcock, Alfred (I)
 *     To Catch a Thief (1955)
 *
 ******************************************************************************/

/**
 *  The {@code DegreesOfSeparation} class provides a client for finding
 *  the degree of separation between one distinguished individual and
 *  every other individual in a social network.
 *  As an example, if the social network consists of actors in which
 *  two actors are connected by a link if they appeared in the same movie,
 *  and Kevin Bacon is the distinguished individual, then the client
 *  computes the Kevin Bacon number of every actor in the network.
 *  <p>
 *  The running time is proportional to the number of individuals and
 *  connections in the network. If the connections are given implicitly,
 *  as in the movie network example (where every two actors are connected
 *  if they appear in the same movie), the efficiency of the algorithm
 *  is improved by allowing both movie and actor vertices and connecting
 *  each movie to all of the actors that appear in that movie.
 *  <p>
 *  For additional documentation,
 *  see <a href="https://algs4.cs.princeton.edu/41graph">Section 4.1</a> of
 *  <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
 *
 *  @author Robert Sedgewick
 *  @author Kevin Wayne
 */
public class DegreesOfSeparation {

    // this class cannot be instantiated
    private DegreesOfSeparation() { }

    /**
     *  Reads in a social network from a file, and then repeatedly reads in
     *  individuals from standard input and prints out their degrees of
     *  separation.
     *  Takes three command-line arguments: the name of a file,
     *  a delimiter, and the name of the distinguished individual.
     *  Each line in the file contains the name of a vertex, followed by a
     *  list of the names of the vertices adjacent to that vertex,
     *  separated by the delimiter.
     *
     * @param args the command-line arguments
     */
    public static void main(String[] args) {
        String filename  = args[0];
        String delimiter = args[1];
        String source    = args[2];

        // StdOut.println("Source: " + source);

        SymbolGraph sg = new SymbolGraph(filename, delimiter);
        Graph G = sg.graph();
        if (!sg.contains(source)) {
            StdOut.println(source + " not in database.");
            return;
        }

        int s = sg.indexOf(source);
        BreadthFirstPaths bfs = new BreadthFirstPaths(G, s);

        while (!StdIn.isEmpty()) {
            String sink = StdIn.readLine();
            if (sg.contains(sink)) {
                int t = sg.indexOf(sink);
                if (bfs.hasPathTo(t)) {
                    for (int v : bfs.pathTo(t)) {
                        StdOut.println("   " + sg.nameOf(v));
                    }
                }
                else {
                    StdOut.println("Not connected");
                }
            }
            else {
                StdOut.println("   Not in database.");
            }
        }
    }
}