Below is the syntax highlighted version of SymbolDigraph.java.
/****************************************************************************** * Compilation: javac SymbolDigraph.java * Execution: java SymbolDigraph * Dependencies: ST.java Digraph.java In.java * Data files: https://algs4.cs.princeton.edu/42digraph/routes.txt * * % java SymbolDigraph routes.txt " " * JFK * MCO * ATL * ORD * ATL * HOU * MCO * LAX * ******************************************************************************/ package edu.princeton.cs.algs4; /** * The {@code SymbolDigraph} class represents a digraph, where the * vertex names are arbitrary strings. * By providing mappings between string vertex names and integers, * it serves as a wrapper around the * {@link Digraph} data type, which assumes the vertex names are integers * between 0 and <em>V</em> - 1. * It also supports initializing a symbol digraph from a file. * <p> * This implementation uses an {@link ST} to map from strings to integers, * an array to map from integers to strings, and a {@link Digraph} to store * the underlying graph. * The <em>indexOf</em> and <em>contains</em> operations take time * proportional to log <em>V</em>, where <em>V</em> is the number of vertices. * The <em>nameOf</em> operation takes constant time. * <p> * For additional documentation, see <a href="https://algs4.cs.princeton.edu/42digraph">Section 4.2</a> of * <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne. * * @author Robert Sedgewick * @author Kevin Wayne */ public class SymbolDigraph { private ST<String, Integer> st; // string -> index private String[] keys; // index -> string private Digraph graph; // the underlying digraph /** * Initializes a digraph from a file using the specified delimiter. * 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 filename the name of the file * @param delimiter the delimiter between fields */ public SymbolDigraph(String filename, String delimiter) { st = new ST<String, Integer>(); // First pass builds the index by reading strings to associate // distinct strings with an index In in = new In(filename); while (in.hasNextLine()) { String[] a = in.readLine().split(delimiter); for (int i = 0; i < a.length; i++) { if (!st.contains(a[i])) st.put(a[i], st.size()); } } // inverted index to get string keys in an array keys = new String[st.size()]; for (String name : st.keys()) { keys[st.get(name)] = name; } // second pass builds the digraph by connecting first vertex on each // line to all others graph = new Digraph(st.size()); in = new In(filename); while (in.hasNextLine()) { String[] a = in.readLine().split(delimiter); int v = st.get(a[0]); for (int i = 1; i < a.length; i++) { int w = st.get(a[i]); graph.addEdge(v, w); } } } /** * Does the digraph contain the vertex named {@code s}? * @param s the name of a vertex * @return {@code true} if {@code s} is the name of a vertex, and {@code false} otherwise */ public boolean contains(String s) { return st.contains(s); } /** * Returns the integer associated with the vertex named {@code s}. * @param s the name of a vertex * @return the integer (between 0 and <em>V</em> - 1) associated with the vertex named {@code s} * @deprecated Replaced by {@link #indexOf(String)}. */ @Deprecated public int index(String s) { return st.get(s); } /** * Returns the integer associated with the vertex named {@code s}. * @param s the name of a vertex * @return the integer (between 0 and <em>V</em> - 1) associated with the vertex named {@code s} */ public int indexOf(String s) { return st.get(s); } /** * Returns the name of the vertex associated with the integer {@code v}. * @param v the integer corresponding to a vertex (between 0 and <em>V</em> - 1) * @return the name of the vertex associated with the integer {@code v} * @throws IllegalArgumentException unless {@code 0 <= v < V} * @deprecated Replaced by {@link #nameOf(int)}. */ @Deprecated public String name(int v) { validateVertex(v); return keys[v]; } /** * Returns the name of the vertex associated with the integer {@code v}. * @param v the integer corresponding to a vertex (between 0 and <em>V</em> - 1) * @return the name of the vertex associated with the integer {@code v} * @throws IllegalArgumentException unless {@code 0 <= v < V} */ public String nameOf(int v) { validateVertex(v); return keys[v]; } /** * Returns the digraph associated with the symbol graph. It is the client's responsibility * not to mutate the digraph. * * @return the digraph associated with the symbol digraph * @deprecated Replaced by {@link #digraph()}. */ @Deprecated public Digraph G() { return graph; } /** * Returns the digraph associated with the symbol graph. It is the client's responsibility * not to mutate the digraph. * * @return the digraph associated with the symbol digraph */ public Digraph digraph() { return graph; } // throw an IllegalArgumentException unless {@code 0 <= v < V} private void validateVertex(int v) { int V = graph.V(); if (v < 0 || v >= V) throw new IllegalArgumentException("vertex " + v + " is not between 0 and " + (V-1)); } /** * Unit tests the {@code SymbolDigraph} data type. * * @param args the command-line arguments */ public static void main(String[] args) { String filename = args[0]; String delimiter = args[1]; SymbolDigraph sg = new SymbolDigraph(filename, delimiter); Digraph graph = sg.digraph(); while (!StdIn.isEmpty()) { String t = StdIn.readLine(); for (int v : graph.adj(sg.index(t))) { StdOut.println(" " + sg.nameOf(v)); } } } } /****************************************************************************** * Copyright 2002-2022, Robert Sedgewick and Kevin Wayne. * * This file is part of algs4.jar, which accompanies the textbook * * Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne, * Addison-Wesley Professional, 2011, ISBN 0-321-57351-X. * http://algs4.cs.princeton.edu * * * algs4.jar is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * algs4.jar is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with algs4.jar. If not, see http://www.gnu.org/licenses. ******************************************************************************/