/******************************************************************************
* Compilation: javac AdjMatrixEdgeWeightedDigraph.java
* Execution: java AdjMatrixEdgeWeightedDigraph V E
* Dependencies: StdOut.java
*
* An edge-weighted digraph, implemented using an adjacency matrix.
* Parallel edges are disallowed; self-loops are allowed.
*
******************************************************************************/
package edu.princeton.cs.algs4;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* The {@code AdjMatrixEdgeWeightedDigraph} class represents a edge-weighted
* digraph of vertices named 0 through <em>V</em> - 1, where each
* directed edge is of type {@link DirectedEdge} and has a real-valued weight.
* It supports the following two primary operations: add a directed edge
* to the digraph and iterate over all of edges incident from a given vertex.
* It also provides
* methods for returning the number of vertices <em>V</em> and the number
* of edges <em>E</em>. Parallel edges are disallowed; self-loops are permitted.
* <p>
* This implementation uses an adjacency-matrix representation.
* All operations take constant time (in the worst case) except
* iterating over the edges incident from a given vertex, which takes
* time proportional to <em>V</em>.
* <p>
* For additional documentation,
* see <a href="http://algs4.cs.princeton.edu/44sp">Section 4.4</a> of
* <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class AdjMatrixEdgeWeightedDigraph {
private static final String NEWLINE = System.getProperty("line.separator");
private final int V;
private int E;
private DirectedEdge[][] adj;
/**
* Initializes an empty edge-weighted digraph with {@code V} vertices and 0 edges.
* @param V the number of vertices
* @throws IllegalArgumentException if {@code V < 0}
*/
public AdjMatrixEdgeWeightedDigraph(int V) {
if (V < 0) throw new IllegalArgumentException("number of vertices must be nonnegative");
this.V = V;
this.E = 0;
this.adj = new DirectedEdge[V][V];
}
/**
* Initializes a random edge-weighted digraph 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 AdjMatrixEdgeWeightedDigraph(int V, int E) {
this(V);
if (E < 0) throw new IllegalArgumentException("number of edges must be nonnegative");
if (E > V*V) throw new IllegalArgumentException("too many edges");
// can be inefficient
while (this.E != E) {
int v = StdRandom.uniform(V);
int w = StdRandom.uniform(V);
double weight = Math.round(100 * StdRandom.uniform()) / 100.0;
addEdge(new DirectedEdge(v, w, weight));
}
}
/**
* Returns the number of vertices in the edge-weighted digraph.
* @return the number of vertices in the edge-weighted digraph
*/
public int V() {
return V;
}
/**
* Returns the number of edges in the edge-weighted digraph.
* @return the number of edges in the edge-weighted digraph
*/
public int E() {
return E;
}
/**
* Adds the directed edge {@code e} to the edge-weighted digraph (if there
* is not already an edge with the same endpoints).
* @param e the edge
*/
public void addEdge(DirectedEdge e) {
int v = e.from();
int w = e.to();
validateVertex(v);
validateVertex(w);
if (adj[v][w] == null) {
E++;
adj[v][w] = e;
}
}
/**
* Returns the directed edges incident from vertex {@code v}.
* @param v the vertex
* @return the directed edges incident from vertex {@code v} as an Iterable
* @throws IllegalArgumentException unless {@code 0 <= v < V}
*/
public Iterable<DirectedEdge> adj(int v) {
validateVertex(v);
return new AdjIterator(v);
}
// support iteration over graph vertices
private class AdjIterator implements Iterator<DirectedEdge>, Iterable<DirectedEdge> {
private int v;
private int w = 0;
public AdjIterator(int v) {
this.v = v;
}
public Iterator<DirectedEdge> iterator() {
return this;
}
public boolean hasNext() {
while (w < V) {
if (adj[v][w] != null) return true;
w++;
}
return false;
}
public DirectedEdge next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
return adj[v][w++];
}
public void remove() {
throw new UnsupportedOperationException();
}
}
/**
* Returns a string representation of the edge-weighted digraph. This method takes
* time proportional to <em>V</em><sup>2</sup>.
* @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 (DirectedEdge e : adj(v)) {
s.append(e + " ");
}
s.append(NEWLINE);
}
return s.toString();
}
// 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));
}
/**
* Unit tests the {@code AdjMatrixEdgeWeightedDigraph} data type.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
int V = Integer.parseInt(args[0]);
int E = Integer.parseInt(args[1]);
AdjMatrixEdgeWeightedDigraph G = new AdjMatrixEdgeWeightedDigraph(V, E);
StdOut.println(G);
}
}
/******************************************************************************
* Copyright 2002-2016, 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.
******************************************************************************/