216 lines
7.6 KiB
Java
216 lines
7.6 KiB
Java
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import edu.princeton.cs.introcs.In;
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import edu.princeton.cs.introcs.StdOut;
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/*************************************************************************
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* Compilation: javac EdgeWeightedDigraph.java
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* Execution: java EdgeWeightedDigraph V E
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* Dependencies: Bag.java DirectedEdge.java
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*
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* An edge-weighted digraph, implemented using adjacency lists.
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*
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*************************************************************************/
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/**
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* The EdgeWeightedDigraph class represents a edge-weighted
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* digraph of vertices named 0 through V - 1, where each
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* directed edge is of type {@link DirectedEdge} and has a real-valued weight.
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* It supports the following two primary operations: add a directed edge
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* to the digraph and iterate over all of edges incident from a given vertex.
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* It also provides
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* methods for returning the number of vertices V and the number
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* of edges E . Parallel edges and self-loops are permitted.
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*
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* This implementation uses an adjacency-lists representation, which
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* is a vertex-indexed array of @link{Bag} objects.
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* All operations take constant time (in the worst case) except
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* iterating over the edges incident from a given vertex, which takes
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* time proportional to the number of such edges.
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*
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* For additional documentation,
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* see <a href="http://algs4.cs.princeton.edu/44sp">Section 4.4</a> of
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* Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
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*
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* @author Robert Sedgewick
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* @author Kevin Wayne
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*/
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public class EdgeWeightedDigraph {
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private final int V;
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private int E;
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private Bag<DirectedEdge>[] adj;
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/**
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* Initializes an empty edge-weighted digraph with V vertices and 0 edges.
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* param V the number of vertices
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* @throws java.lang.IllegalArgumentException if V < 0
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*/
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public EdgeWeightedDigraph(int V) {
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if (V < 0) throw new IllegalArgumentException("Number of vertices in a Digraph must be nonnegative");
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this.V = V;
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this.E = 0;
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adj = (Bag<DirectedEdge>[]) new Bag[V];
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for (int v = 0; v < V; v++)
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adj[v] = new Bag<DirectedEdge>();
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}
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/**
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* Initializes a random edge-weighted digraph with V vertices and E edges.
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* param V the number of vertices
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* param E the number of edges
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* @throws java.lang.IllegalArgumentException if V < 0
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* @throws java.lang.IllegalArgumentException if E < 0
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*/
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public EdgeWeightedDigraph(int V, int E) {
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this(V);
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if (E < 0) throw new IllegalArgumentException("Number of edges in a Digraph must be nonnegative");
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for (int i = 0; i < E; i++) {
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int v = (int) (Math.random() * V);
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int w = (int) (Math.random() * V);
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double weight = Math.round(100 * Math.random()) / 100.0;
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DirectedEdge e = new DirectedEdge(v, w, weight);
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addEdge(e);
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}
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}
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/**
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* Initializes an edge-weighted digraph from an input stream.
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* The format is the number of vertices V ,
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* followed by the number of edges E ,
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* followed by E pairs of vertices and edge weights,
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* with each entry separated by whitespace.
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* @param in the input stream
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* @throws java.lang.IndexOutOfBoundsException if the endpoints of any edge are not in prescribed range
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* @throws java.lang.IllegalArgumentException if the number of vertices or edges is negative
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*/
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public EdgeWeightedDigraph(In in) {
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this(in.readInt());
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int E = in.readInt();
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if (E < 0) throw new IllegalArgumentException("Number of edges must be nonnegative");
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for (int i = 0; i < E; i++) {
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int v = in.readInt();
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int w = in.readInt();
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if (v < 0 || v >= V) throw new IndexOutOfBoundsException("vertex " + v + " is not between 0 and " + (V-1));
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if (w < 0 || w >= V) throw new IndexOutOfBoundsException("vertex " + w + " is not between 0 and " + (V-1));
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double weight = in.readDouble();
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addEdge(new DirectedEdge(v, w, weight));
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}
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}
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/**
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* Initializes a new edge-weighted digraph that is a deep copy of G .
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* @param G the edge-weighted graph to copy
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*/
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public EdgeWeightedDigraph(EdgeWeightedDigraph G) {
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this(G.V());
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this.E = G.E();
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for (int v = 0; v < G.V(); v++) {
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// reverse so that adjacency list is in same order as original
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Stack<DirectedEdge> reverse = new Stack<DirectedEdge>();
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for (DirectedEdge e : G.adj[v]) {
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reverse.push(e);
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}
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for (DirectedEdge e : reverse) {
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adj[v].add(e);
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}
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}
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}
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/**
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* Returns the number of vertices in the edge-weighted digraph.
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* @return the number of vertices in the edge-weighted digraph
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*/
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public int V() {
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return V;
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}
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/**
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* Returns the number of edges in the edge-weighted digraph.
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* @return the number of edges in the edge-weighted digraph
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*/
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public int E() {
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return E;
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}
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/**
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* Adds the directed edge e to the edge-weighted digraph.
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* @param e the edge
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*/
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public void addEdge(DirectedEdge e) {
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int v = e.from();
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adj[v].add(e);
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E++;
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}
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/**
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* Returns the directed edges incident from vertex v .
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* @return the directed edges incident from vertex v as an Iterable
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* @param v the vertex
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* @throws java.lang.IndexOutOfBoundsException unless 0 <= v < V
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*/
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public Iterable<DirectedEdge> adj(int v) {
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if (v < 0 || v >= V) throw new IndexOutOfBoundsException("vertex " + v + " is not between 0 and " + (V-1));
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return adj[v];
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}
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/**
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* Returns all directed edges in the edge-weighted digraph.
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* To iterate over the edges in the edge-weighted graph, use foreach notation:
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* for (DirectedEdge e : G.edges()) .
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* @return all edges in the edge-weighted graph as an Iterable.
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*/
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public Iterable<DirectedEdge> edges() {
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Bag<DirectedEdge> list = new Bag<DirectedEdge>();
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for (int v = 0; v < V; v++) {
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for (DirectedEdge e : adj(v)) {
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list.add(e);
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}
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}
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return list;
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}
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/**
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* Returns the number of directed edges incident from vertex v .
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* This is known as the outdegree of vertex v .
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* @return the number of directed edges incident from vertex v
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* @param v the vertex
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* @throws java.lang.IndexOutOfBoundsException unless 0 <= v < V
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*/
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public int outdegree(int v) {
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if (v < 0 || v >= V) throw new IndexOutOfBoundsException("vertex " + v + " is not between 0 and " + (V-1));
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return adj[v].size();
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}
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/**
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* Returns a string representation of the edge-weighted digraph.
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* This method takes time proportional to E + V .
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* @return the number of vertices V , followed by the number of edges E ,
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* followed by the V adjacency lists of edges
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*/
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@Override
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public String toString() {
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String NEWLINE = System.getProperty("line.separator");
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StringBuilder s = new StringBuilder();
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s.append(V + " " + E + NEWLINE);
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for (int v = 0; v < V; v++) {
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s.append(v + ": ");
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for (DirectedEdge e : adj[v]) {
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s.append(e + " ");
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}
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s.append(NEWLINE);
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}
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return s.toString();
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}
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/**
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* Unit tests the EdgeWeightedDigraph data type.
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*/
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public static void main(String[] args) {
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In in = new In(args[0]);
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EdgeWeightedDigraph G = new EdgeWeightedDigraph(in);
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StdOut.println(G);
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}
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}
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