``` 001 002 003 004 005 006 007 008 009 010 011 012 013 014 015 016 017 018 019 020 021 022 023 024 025 026 027 028 029 030 031 032 033 034 035 036 037 038 039 040 041 042 043 044 045 046 047 048 049 050 051 052 053 054 055 056 057 058 059 060 061 062 063 064 065 066 067 068 069 070 071 072 073 074 075 076 077 078 079 080 081 082 083 084 085 086 087 088 089 090 091 092 093 094 095 096 097 098 099 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 ``` ```// Exercise 4.1.3 (Solution published at http://algs4.cs.princeton.edu/) package algs41; import stdlib.*; import algs13.Bag; import algs13.Stack; /** * The Graph class represents an undirected graph of vertices * named 0 through V-1. * It supports the following operations: add an edge to the graph, * iterate over all of the neighbors adjacent to a vertex. * Parallel edges and self-loops are permitted. *

* For additional documentation, see Section 5.1 of * Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne. */ public class Graph { private final int V; private int E; private final Bag[] adj; /** * Create an empty graph with V vertices. */ @SuppressWarnings("unchecked") public Graph(int V) { if (V < 0) throw new Error("Number of vertices must be nonnegative"); this.V = V; this.E = 0; this.adj = new Bag[V]; for (int v = 0; v < V; v++) { adj[v] = new Bag<>(); } } /** * Create a random graph with V vertices and E edges with no parallel edges or self loops. * Expected running time is proportional to V + E. */ public Graph(int V, int E) { this (V, E, false); } /** * Create a random graph with V vertices and E edges. * Expected running time is proportional to V + E. */ public Graph(int V, int E, boolean allowParallelEdgesAndSelfLoops) { this(V); if (E < 0) throw new Error("Number of edges must be nonnegative"); if (allowParallelEdgesAndSelfLoops) { for (int i = 0; i < E; i++) { int v = (int) (Math.random() * V); int w = (int) (Math.random() * V); addEdge(v, w); } } else { if (E > V*(V-1)/2) throw new Error("Number of edges must be less than V*(V-1)/2"); newEdge: while (E>0) { int v = (int) (Math.random() * V); int w = (int) (Math.random() * V); if (v == w) continue; for (int w2 : adj[v]) if (w == w2) continue newEdge; addEdge(v, w); E--; } } } /** * Create a graph from input stream. */ public Graph(In in) { this(in.readInt()); int E = in.readInt(); for (int i = 0; i < E; i++) { int v = in.readInt(); int w = in.readInt(); addEdge(v, w); } } /** * Copy constructor. */ public Graph(Graph 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 reverse = new Stack<>(); for (int w : G.adj[v]) { reverse.push(w); } for (int w : reverse) { adj[v].add(w); } } } /** * Return the number of vertices in the graph. */ public int V() { return V; } /** * Return the number of edges in the graph. */ public int E() { return E; } /** * Add the undirected edge v-w to graph. * @throws java.lang.IndexOutOfBoundsException unless both 0 <= v < V and 0 <= w < V */ public void addEdge(int v, int w) { if (v < 0 || v >= V) throw new IndexOutOfBoundsException(); if (w < 0 || w >= V) throw new IndexOutOfBoundsException(); E++; adj[v].add(w); adj[w].add(v); } /** * Return the list of neighbors of vertex v as in Iterable. * @throws java.lang.IndexOutOfBoundsException unless 0 <= v < V */ public Iterable adj(int v) { if (v < 0 || v >= V) throw new IndexOutOfBoundsException(); return adj[v]; } /** * Return a string representation of the graph. */ public String toString() { StringBuilder s = new StringBuilder(); String NEWLINE = System.getProperty("line.separator"); s.append(V + " vertices, " + E + " edges " + NEWLINE); for (int v = 0; v < V; v++) { s.append(v + ": "); for (int w : adj[v]) { s.append(w + " "); } s.append(NEWLINE); } return s.toString(); } /** * Save a graphviz representation of the graph. * See graphviz.org. */ public void toGraphviz(String filename) { GraphvizBuilder gb = new GraphvizBuilder (); for (int v = 0; v < V; v++) { gb.addNode (v); boolean showSelfLoop = false; for (int w : adj[v]) { if (v < w) // only once each edge gb.addEdge (v, w); if (v == w) { showSelfLoop = !showSelfLoop; if (showSelfLoop) gb.addEdge (v, w); } } } gb.toFileUndirected (filename); } /** * Test client. */ public static void main(String[] args) { args = new String [] { "data/tinyCG.txt" }; //args = new String [] { "data/tinyG.txt" }; args = new String [] { "20", "40" }; Graph G; if (args.length == 1) { In in = new In(args[0]); G = new Graph(in); } else { int V = Integer.parseInt (args[0]); int E = Integer.parseInt (args[1]); G = new Graph(V, E, false); } StdOut.println(G); G.toGraphviz ("g.png"); } } ```