edu.princeton.cs.algs4.EdgeWeightedDigraph Maven / Gradle / Ivy
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/******************************************************************************
* Compilation: javac EdgeWeightedDigraph.java
* Execution: java EdgeWeightedDigraph digraph.txt
* Dependencies: Bag.java DirectedEdge.java
* Data files: https://algs4.cs.princeton.edu/44st/tinyEWD.txt
* https://algs4.cs.princeton.edu/44st/mediumEWD.txt
* https://algs4.cs.princeton.edu/44st/largeEWD.txt
*
* An edge-weighted digraph, implemented using adjacency lists.
*
******************************************************************************/
package edu.princeton.cs.algs4;
/**
* The {@code EdgeWeightedDigraph} class represents a edge-weighted
* digraph of vertices named 0 through V - 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 V and the number
* of edges E. Parallel edges and self-loops are permitted.
*
* This implementation uses an adjacency-lists representation, which
* is a vertex-indexed array of {@link Bag} objects.
* All operations take constant time (in the worst case) except
* iterating over the edges incident from a given vertex, which takes
* time proportional to the number of such edges.
*
* For additional documentation,
* see Section 4.4 of
* Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class EdgeWeightedDigraph {
private static final String NEWLINE = System.getProperty("line.separator");
private final int V; // number of vertices in this digraph
private int E; // number of edges in this digraph
private Bag[] adj; // adj[v] = adjacency list for vertex v
private int[] indegree; // indegree[v] = indegree of vertex v
/**
* 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 EdgeWeightedDigraph(int V) {
if (V < 0) throw new IllegalArgumentException("Number of vertices in a Digraph must be nonnegative");
this.V = V;
this.E = 0;
this.indegree = new int[V];
adj = (Bag[]) new Bag[V];
for (int v = 0; v < V; v++)
adj[v] = new Bag();
}
/**
* Initializes a random edge-weighted digraph with {@code V} vertices and E 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 EdgeWeightedDigraph(int V, int E) {
this(V);
if (E < 0) throw new IllegalArgumentException("Number of edges in a Digraph must be nonnegative");
for (int i = 0; i < E; i++) {
int v = StdRandom.uniform(V);
int w = StdRandom.uniform(V);
double weight = 0.01 * StdRandom.uniform(100);
DirectedEdge e = new DirectedEdge(v, w, weight);
addEdge(e);
}
}
/**
* Initializes an edge-weighted digraph from the specified input stream.
* The format is the number of vertices V,
* followed by the number of edges E,
* followed by E pairs of vertices and edge weights,
* with each entry separated by whitespace.
*
* @param in the input stream
* @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 EdgeWeightedDigraph(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();
validateVertex(v);
validateVertex(w);
double weight = in.readDouble();
addEdge(new DirectedEdge(v, w, weight));
}
}
/**
* Initializes a new edge-weighted digraph that is a deep copy of {@code G}.
*
* @param G the edge-weighted digraph to copy
*/
public EdgeWeightedDigraph(EdgeWeightedDigraph G) {
this(G.V());
this.E = G.E();
for (int v = 0; v < G.V(); v++)
this.indegree[v] = G.indegree(v);
for (int v = 0; v < G.V(); v++) {
// reverse so that adjacency list is in same order as original
Stack reverse = new Stack();
for (DirectedEdge e : G.adj[v]) {
reverse.push(e);
}
for (DirectedEdge e : reverse) {
adj[v].add(e);
}
}
}
/**
* Returns the number of vertices in this edge-weighted digraph.
*
* @return the number of vertices in this edge-weighted digraph
*/
public int V() {
return V;
}
/**
* Returns the number of edges in this edge-weighted digraph.
*
* @return the number of edges in this edge-weighted digraph
*/
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 directed edge {@code e} to this edge-weighted digraph.
*
* @param e the edge
* @throws IllegalArgumentException unless endpoints of edge are between {@code 0}
* and {@code V-1}
*/
public void addEdge(DirectedEdge e) {
int v = e.from();
int w = e.to();
validateVertex(v);
validateVertex(w);
adj[v].add(e);
indegree[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 adj(int v) {
validateVertex(v);
return adj[v];
}
/**
* Returns the number of directed edges incident from vertex {@code v}.
* This is known as the outdegree of vertex {@code v}.
*
* @param v the vertex
* @return the outdegree of vertex {@code v}
* @throws IllegalArgumentException unless {@code 0 <= v < V}
*/
public int outdegree(int v) {
validateVertex(v);
return adj[v].size();
}
/**
* Returns the number of directed edges incident to vertex {@code v}.
* This is known as the indegree of vertex {@code v}.
*
* @param v the vertex
* @return the indegree of vertex {@code v}
* @throws IllegalArgumentException unless {@code 0 <= v < V}
*/
public int indegree(int v) {
validateVertex(v);
return indegree[v];
}
/**
* Returns all directed edges in this edge-weighted digraph.
* To iterate over the edges in this edge-weighted digraph, use foreach notation:
* {@code for (DirectedEdge e : G.edges())}.
*
* @return all edges in this edge-weighted digraph, as an iterable
*/
public Iterable edges() {
Bag list = new Bag();
for (int v = 0; v < V; v++) {
for (DirectedEdge e : adj(v)) {
list.add(e);
}
}
return list;
}
/**
* Returns a string representation of this edge-weighted digraph.
*
* @return the number of vertices V, followed by the number of edges E,
* followed by the V 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();
}
/**
* Unit tests the {@code EdgeWeightedDigraph} data type.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
In in = new In(args[0]);
EdgeWeightedDigraph G = new EdgeWeightedDigraph(in);
StdOut.println(G);
}
}
/******************************************************************************
* Copyright 2002-2018, 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.
******************************************************************************/