Below is the syntax highlighted version of EdgeWeightedGraph.java.
/****************************************************************************** * Compilation: javac EdgeWeightedGraph.java * Execution: java EdgeWeightedGraph filename.txt * Dependencies: Bag.java Edge.java In.java StdOut.java * Data files: https://algs4.cs.princeton.edu/43mst/tinyEWG.txt * https://algs4.cs.princeton.edu/43mst/mediumEWG.txt * https://algs4.cs.princeton.edu/43mst/largeEWG.txt * * An edge-weighted undirected graph, implemented using adjacency lists. * Parallel edges and self-loops are permitted. * * % java EdgeWeightedGraph tinyEWG.txt * 8 16 * 0: 6-0 0.58000 0-2 0.26000 0-4 0.38000 0-7 0.16000 * 1: 1-3 0.29000 1-2 0.36000 1-7 0.19000 1-5 0.32000 * 2: 6-2 0.40000 2-7 0.34000 1-2 0.36000 0-2 0.26000 2-3 0.17000 * 3: 3-6 0.52000 1-3 0.29000 2-3 0.17000 * 4: 6-4 0.93000 0-4 0.38000 4-7 0.37000 4-5 0.35000 * 5: 1-5 0.32000 5-7 0.28000 4-5 0.35000 * 6: 6-4 0.93000 6-0 0.58000 3-6 0.52000 6-2 0.40000 * 7: 2-7 0.34000 1-7 0.19000 0-7 0.16000 5-7 0.28000 4-7 0.37000 * ******************************************************************************/ package edu.princeton.cs.algs4; import java.util.NoSuchElementException; /** * The {@code EdgeWeightedGraph} class represents an edge-weighted * graph of vertices named 0 through <em>V</em> – 1, where each * undirected edge is of type {@link Edge} and has a real-valued weight. * It supports the following two primary operations: add an edge to the graph, * iterate over all of the edges incident to a vertex. It also provides * methods for returning the degree of a vertex, the number of vertices * <em>V</em> in the graph, and the number of edges <em>E</em> in the graph. * Parallel edges and self-loops are permitted. * By convention, a self-loop <em>v</em>-<em>v</em> appears in the * adjacency list of <em>v</em> twice and contributes two to the degree * of <em>v</em>. * <p> * This implementation uses an <em>adjacency-lists representation</em>, which * is a vertex-indexed array of {@link Bag} objects. * It uses Θ(<em>E</em> + <em>V</em>) space, where <em>E</em> is * the number of edges and <em>V</em> is the number of vertices. * All instance methods take Θ(1) time. (Though, iterating over * the edges returned by {@link #adj(int)} takes time proportional * to the degree of the vertex.) * Constructing an empty edge-weighted graph with <em>V</em> vertices takes * Θ(<em>V</em>) time; constructing an edge-weighted graph with * <em>E</em> edges and <em>V</em> vertices takes * Θ(<em>E</em> + <em>V</em>) time. * <p> * For additional documentation, * see <a href="https://algs4.cs.princeton.edu/43mst">Section 4.3</a> of * <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne. * * @author Robert Sedgewick * @author Kevin Wayne */ public class EdgeWeightedGraph { private static final String NEWLINE = System.getProperty("line.separator"); private final int V; private int E; private Bag<Edge>[] adj; /** * Initializes an empty edge-weighted graph with {@code V} vertices and 0 edges. * * @param V the number of vertices * @throws IllegalArgumentException if {@code V < 0} */ public EdgeWeightedGraph(int V) { if (V < 0) throw new IllegalArgumentException("Number of vertices must be non-negative"); this.V = V; this.E = 0; adj = (Bag<Edge>[]) new Bag[V]; for (int v = 0; v < V; v++) { adj[v] = new Bag<Edge>(); } } /** * Initializes a random edge-weighted graph with {@code V} vertices and <em>E</em> edges. * * @param V the number of vertices * @param E the number of edges * @throws IllegalArgumentException if {@code V < 0} * @throws IllegalArgumentException if {@code E < 0} */ public EdgeWeightedGraph(int V, int E) { this(V); if (E < 0) throw new IllegalArgumentException("Number of edges must be non-negative"); for (int i = 0; i < E; i++) { int v = StdRandom.uniformInt(V); int w = StdRandom.uniformInt(V); double weight = 0.01 * StdRandom.uniformInt(0, 100); Edge e = new Edge(v, w, weight); addEdge(e); } } /** * Initializes an edge-weighted graph from an input stream. * The format is the number of vertices <em>V</em>, * followed by the number of edges <em>E</em>, * followed by <em>E</em> pairs of vertices and edge weights, * with each entry separated by whitespace. * * @param in the input stream * @throws IllegalArgumentException if {@code in} is {@code null} * @throws IllegalArgumentException if the endpoints of any edge are not in prescribed range * @throws IllegalArgumentException if the number of vertices or edges is negative */ public EdgeWeightedGraph(In in) { if (in == null) throw new IllegalArgumentException("argument is null"); try { V = in.readInt(); adj = (Bag<Edge>[]) new Bag[V]; for (int v = 0; v < V; v++) { adj[v] = new Bag<Edge>(); } int E = in.readInt(); if (E < 0) throw new IllegalArgumentException("Number of edges must be non-negative"); for (int i = 0; i < E; i++) { int v = in.readInt(); int w = in.readInt(); validateVertex(v); validateVertex(w); double weight = in.readDouble(); Edge e = new Edge(v, w, weight); addEdge(e); } } catch (NoSuchElementException e) { throw new IllegalArgumentException("invalid input format in EdgeWeightedGraph constructor", e); } } /** * Initializes a new edge-weighted graph that is a deep copy of {@code G}. * * @param G the edge-weighted graph to copy */ public EdgeWeightedGraph(EdgeWeightedGraph G) { this(G.V()); this.E = G.E(); for (int v = 0; v < G.V(); v++) { // reverse so that adjacency list is in same order as original Stack<Edge> reverse = new Stack<Edge>(); for (Edge e : G.adj[v]) { reverse.push(e); } for (Edge e : reverse) { adj[v].add(e); } } } /** * Returns the number of vertices in this edge-weighted graph. * * @return the number of vertices in this edge-weighted graph */ public int V() { return V; } /** * Returns the number of edges in this edge-weighted graph. * * @return the number of edges in this edge-weighted graph */ public int E() { return E; } // throw an IllegalArgumentException unless {@code 0 <= v < V} private void validateVertex(int v) { if (v < 0 || v >= V) throw new IllegalArgumentException("vertex " + v + " is not between 0 and " + (V-1)); } /** * Adds the undirected edge {@code e} to this edge-weighted graph. * * @param e the edge * @throws IllegalArgumentException unless both endpoints are between {@code 0} and {@code V-1} */ public void addEdge(Edge e) { int v = e.either(); int w = e.other(v); validateVertex(v); validateVertex(w); adj[v].add(e); adj[w].add(e); E++; } /** * Returns the edges incident on vertex {@code v}. * * @param v the vertex * @return the edges incident on vertex {@code v} as an Iterable * @throws IllegalArgumentException unless {@code 0 <= v < V} */ public Iterable<Edge> adj(int v) { validateVertex(v); return adj[v]; } /** * Returns the degree of vertex {@code v}. * * @param v the vertex * @return the degree of vertex {@code v} * @throws IllegalArgumentException unless {@code 0 <= v < V} */ public int degree(int v) { validateVertex(v); return adj[v].size(); } /** * Returns all edges in this edge-weighted graph. * To iterate over the edges in this edge-weighted graph, use foreach notation: * {@code for (Edge e : G.edges())}. * * @return all edges in this edge-weighted graph, as an iterable */ public Iterable<Edge> edges() { Bag<Edge> list = new Bag<Edge>(); for (int v = 0; v < V; v++) { int selfLoops = 0; for (Edge e : adj(v)) { if (e.other(v) > v) { list.add(e); } // add only one copy of each self loop (self loops will be consecutive) else if (e.other(v) == v) { if (selfLoops % 2 == 0) list.add(e); selfLoops++; } } } return list; } /** * Returns a string representation of the edge-weighted graph. * This method takes time proportional to <em>E</em> + <em>V</em>. * * @return the number of vertices <em>V</em>, followed by the number of edges <em>E</em>, * followed by the <em>V</em> adjacency lists of edges */ public String toString() { StringBuilder s = new StringBuilder(); s.append(V + " " + E + NEWLINE); for (int v = 0; v < V; v++) { s.append(v + ": "); for (Edge e : adj[v]) { s.append(e + " "); } s.append(NEWLINE); } return s.toString(); } /** * Unit tests the {@code EdgeWeightedGraph} data type. * * @param args the command-line arguments */ public static void main(String[] args) { In in = new In(args[0]); EdgeWeightedGraph G = new EdgeWeightedGraph(in); StdOut.println(G); } } /****************************************************************************** * 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. ******************************************************************************/