BaconHistogram.java

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

/******************************************************************************
 *  Compilation:  javac BaconHistogram.java
 *  Execution:    java BaconHistogram input.txt delimiter actor
 *  Dependencies: SymbolGraph.java Graph.java In.java BreadthFirstPaths.java
 *  Data files:   https://algs4.cs.princeton.edu/41graph/movies.txt
 *
 *  Reads in a data file containing movie records (a movie followed by a list
 *  of actors appearing in that movie), and runs breadth first search to
 *  find the shortest distance from the source (Kevin Bacon) to each other
 *  actor and movie. After computing the Kevin Bacon numbers, the programs
 *  prints a histogram of the number of actors with each Kevin Bacon number.
 *
 *
 *  % java BaconHistogram movies.txt "/" "Bacon, Kevin"
 *    0        1
 *    1     1324
 *    2    70717
 *    3    40862
 *    4     1591
 *    5      125
 *  Inf        0
 *
 *  Remark: hard to identify actors with infinite bacon numbers because
 *  we can't tell whether an unreachable vertex is an actor or movie.
 *
 ******************************************************************************/

public class BaconHistogram {
    public static void main(String[] args) {
        String filename  = args[0];
        String delimiter = args[1];
        String source    = args[2];

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

        // run breadth-first search from s
        int s = sg.indexOf(source);
        BreadthFirstPaths bfs = new BreadthFirstPaths(G, s);


        // compute histogram of Kevin Bacon numbers - 100 for infinity
        int MAX_BACON = 100;
        int[] hist = new int[MAX_BACON + 1];
        for (int v = 0; v < G.V(); v++) {
            int bacon = Math.min(MAX_BACON, bfs.distTo(v));
            hist[bacon]++;

            // to print actors and movies with large bacon numbers
            if (bacon/2 >= 7 && bacon < MAX_BACON)
                StdOut.printf("%d %s\n", bacon/2, sg.nameOf(v));
        }

        // print out histogram - even indices are actors
        for (int i = 0; i < MAX_BACON; i += 2) {
            if (hist[i] == 0) break;
            StdOut.printf("%3d %8d\n", i/2, hist[i]);
        }
        StdOut.printf("Inf %8d\n", hist[MAX_BACON]);
    }
}