package edu.princeton.cs.algs4.ch41;
import edu.princeton.cs.algs4.ch13.Bag;
import edu.princeton.cs.algs4.ch13.Stack;
import edu.princeton.cs.introcs.*;
/*************************************************************************
* Compilation: javac Graph.java
* Execution: java Graph input.txt
* Dependencies: Bag.java In.java StdOut.java
* Data files: http://algs4.cs.princeton.edu/41undirected/tinyG.txt
*
* A graph, implemented using an array of sets.
* Parallel edges and self-loops allowed.
*
* % java Graph tinyG.txt
* 13 vertices, 13 edges
* 0: 6 2 1 5
* 1: 0
* 2: 0
* 3: 5 4
* 4: 5 6 3
* 5: 3 4 0
* 6: 0 4
* 7: 8
* 8: 7
* 9: 11 10 12
* 10: 9
* 11: 9 12
* 12: 11 9
*
* % java Graph mediumG.txt
* 250 vertices, 1273 edges
* 0: 225 222 211 209 204 202 191 176 163 160 149 114 97 80 68 59 58 49 44 24 15
* 1: 220 203 200 194 189 164 150 130 107 72
* 2: 141 110 108 86 79 51 42 18 14
* ...
*
*************************************************************************/
/**
* The <tt>Graph</tt> class represents an undirected graph of vertices
* named 0 through <em>V</em> - 1.
* It supports the following two primary operations: add an edge to the graph,
* iterate over all of the vertices adjacent to a vertex. It also provides
* methods for returning the number of vertices <em>V</em> and the number
* of edges <em>E</em>. Parallel edges and self-loops are permitted.
* <p>
* This implementation uses an adjacency-lists representation, which
* is a vertex-indexed array of {@link edu.princeton.cs.algs4.ch13.Bag} objects.
* All operations take constant time (in the worst case) except
* iterating over the vertices adjacent to a given vertex, which takes
* time proportional to the number of such vertices.
* <p>
* For additional documentation, see <a href="http://algs4.cs.princeton.edu/41undirected">Section 4.1</a> of
* <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class Graph {
private final int V;
private int E;
private Bag<Integer>[] adj;
/**
* Initializes an empty graph with <tt>V</tt> vertices and 0 edges.
* param V the number of vertices
* @throws java.lang.IllegalArgumentException if <tt>V</tt> < 0
*/
public Graph(int V) {
if (V < 0) throw new IllegalArgumentException("Number of vertices must be nonnegative");
this.V = V;
this.E = 0;
adj = (Bag<Integer>[]) new Bag[V];
for (int v = 0; v < V; v++) {
adj[v] = new Bag<Integer>();
}
}
/**
* Initializes a 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, with each entry separated by whitespace.
* @param in the input stream
* @throws java.lang.IndexOutOfBoundsException if the endpoints of any edge are not in prescribed range
* @throws java.lang.IllegalArgumentException if the number of vertices or edges is negative
*/
public Graph(In in) {
this(in.readInt());
int E = in.readInt();
if (E < 0) throw new IllegalArgumentException("Number of edges must be nonnegative");
for (int i = 0; i < E; i++) {
int v = in.readInt();
int w = in.readInt();
addEdge(v, w);
}
}
/**
* Initializes a new graph that is a deep copy of <tt>G</tt>.
* @param G the graph to copy
*/
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<Integer> reverse = new Stack<Integer>();
for (int w : G.adj[v]) {
reverse.push(w);
}
for (int w : reverse) {
adj[v].add(w);
}
}
}
/**
* Returns the number of vertices in the graph.
* @return the number of vertices in the graph
*/
public int V() {
return V;
}
/**
* Returns the number of edges in the graph.
* @return the number of edges in the graph
*/
public int E() {
return E;
}
// throw an IndexOutOfBoundsException unless 0 <= v < V
private void validateVertex(int v) {
if (v < 0 || v >= V)
throw new IndexOutOfBoundsException("vertex " + v + " is not between 0 and " + (V-1));
}
/**
* Adds the undirected edge v-w to the graph.
* @param v one vertex in the edge
* @param w the other vertex in the edge
* @throws java.lang.IndexOutOfBoundsException unless both 0 <= v < V and 0 <= w < V
*/
public void addEdge(int v, int w) {
validateVertex(v);
validateVertex(w);
E++;
adj[v].add(w);
adj[w].add(v);
}
/**
* Returns the vertices adjacent to vertex <tt>v</tt>.
* @return the vertices adjacent to vertex <tt>v</tt> as an Iterable
* @param v the vertex
* @throws java.lang.IndexOutOfBoundsException unless 0 <= v < V
*/
public Iterable<Integer> adj(int v) {
validateVertex(v);
return adj[v];
}
/**
* Returns the degree of vertex <tt>v</tt>.
* @return the degree of vertex <tt>v</tt>
* @param v the vertex
* @throws java.lang.IndexOutOfBoundsException unless 0 <= v < V
*/
public int degree(int v) {
validateVertex(v);
return adj[v].size();
}
/**
* Returns a string representation of the 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
*/
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();
}
/**
* Unit tests the <tt>Graph</tt> data type.
*/
public static void main(String[] args) {
In in = new In(args[0]);
Graph G = new Graph(in);
StdOut.println(G);
}
}
/*************************************************************************
* Copyright 2002-2012, Robert Sedgewick and Kevin Wayne.
*
* This file is part of algs4-package.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-package.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-package.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-package.jar. If not, see http://www.gnu.org/licenses.
*************************************************************************/