// This program reads a Graphviz graph file of friendships and prints the set
// of friends for each person.

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

public class Friends1 {
    public static void main(String[] args) throws FileNotFoundException {
        Scanner input = new Scanner(new File("friends.dot"));
        Map<String, Set<String>> friends = readFile(input);
        for (String name : friends.keySet()) {
            System.out.printf("%-12s => maps to => %s\n", name,
                              friends.get(name).toString());
        }
    }

    // pre : input is open and contains a legal Graphviz file of friendship
    //       connections where each friend is listed as a single token
    // post: returns a map that contains for each person the set of friends for
    //       that person
    public static Map<String, Set<String>> readFile(Scanner input) {
        Map<String, Set<String>> friends = new TreeMap<String, Set<String>>();
        while (input.hasNextLine()) {
            String line = input.nextLine();
            if (line.contains("--")) {
                Scanner lineData = new Scanner(line);
                String name1 = lineData.next();
                lineData.next();  // this skips the "--" token
                String name2 = lineData.next();
                addTo(friends, name1, name2);
                addTo(friends, name2, name1);
            }
        }
        return friends;
    }

    // post: records a friendship for name1.  If name1 is not in the map, a new
    //       set is added to the map
    public static void addTo(Map<String, Set<String>> friends, String name1, 
                             String name2) {
        if (!friends.containsKey(name1)) {
            friends.put(name1, new TreeSet<String>());
        }
        friends.get(name1).add(name2);
    }
}