212 lines
6.5 KiB
Java
212 lines
6.5 KiB
Java
|
|
|
|
/*************************************************************************
|
|
* Compilation: javac Digraph.java
|
|
* Execution: java Digraph filename.txt
|
|
* Dependencies: Bag.java In.java StdOut.java
|
|
* Data files: http://algs4.cs.princeton.edu/42directed/tinyDG.txt
|
|
*
|
|
* A graph, implemented using an array of lists.
|
|
* Parallel edges and self-loops are permitted.
|
|
*
|
|
* % java Digraph tinyDG.txt
|
|
* 13 vertices, 22 edges
|
|
* 0: 5 1
|
|
* 1:
|
|
* 2: 0 3
|
|
* 3: 5 2
|
|
* 4: 3 2
|
|
* 5: 4
|
|
* 6: 9 4 8 0
|
|
* 7: 6 9
|
|
* 8: 6
|
|
* 9: 11 10
|
|
* 10: 12
|
|
* 11: 4 12
|
|
* 12: 9
|
|
*
|
|
*************************************************************************/
|
|
|
|
import java.util.InputMismatchException;
|
|
import java.util.NoSuchElementException;
|
|
|
|
import edu.princeton.cs.introcs.In;
|
|
import edu.princeton.cs.introcs.StdOut;
|
|
|
|
/**
|
|
* The Digraph class represents a directed graph of vertices
|
|
* named 0 through V - 1.
|
|
* It supports the following two primary operations: add an edge to the digraph,
|
|
* iterate over all of the vertices adjacent from a given vertex.
|
|
* 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 vertices adjacent from a given vertex, which takes
|
|
* time proportional to the number of such vertices.
|
|
*
|
|
* For additional documentation,
|
|
* see <a href="http://algs4.cs.princeton.edu/42directed">Section 4.2</a> of
|
|
* Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
|
|
*
|
|
* @author Robert Sedgewick
|
|
* @author Kevin Wayne
|
|
*/
|
|
|
|
public class Digraph {
|
|
private final int V;
|
|
private int E;
|
|
private Bag<Integer>[] adj;
|
|
|
|
/**
|
|
* Initializes an empty digraph with V vertices.
|
|
* @param V the number of vertices
|
|
* @throws java.lang.IllegalArgumentException if V < 0
|
|
*/
|
|
public Digraph(int V) {
|
|
if (V < 0) throw new IllegalArgumentException("Number of vertices in a Digraph 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 digraph from an input stream.
|
|
* The format is the number of vertices V ,
|
|
* followed by the number of edges E ,
|
|
* followed by E 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 Digraph(In in) {
|
|
try {
|
|
this.V = in.readInt();
|
|
if (V < 0) throw new IllegalArgumentException("Number of vertices in a Digraph must be nonnegative");
|
|
adj = (Bag<Integer>[]) new Bag[V];
|
|
for (int v = 0; v < V; v++) {
|
|
adj[v] = new Bag<Integer>();
|
|
}
|
|
int E = in.readInt();
|
|
if (E < 0) throw new IllegalArgumentException("Number of edges in a Digraph must be nonnegative");
|
|
for (int i = 0; i < E; i++) {
|
|
int v = in.readInt();
|
|
int w = in.readInt();
|
|
addEdge(v, w);
|
|
}
|
|
}
|
|
catch (NoSuchElementException e) {
|
|
throw new InputMismatchException("Invalid input format in Digraph constructor");
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Initializes a new digraph that is a deep copy of G .
|
|
* @param G the digraph to copy
|
|
*/
|
|
public Digraph(Digraph 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 digraph.
|
|
* @return the number of vertices in the digraph
|
|
*/
|
|
public int V() {
|
|
return V;
|
|
}
|
|
|
|
/**
|
|
* Returns the number of edges in the digraph.
|
|
* @return the number of edges in the digraph
|
|
*/
|
|
public int E() {
|
|
return E;
|
|
}
|
|
|
|
|
|
/**
|
|
* Adds the directed edge v->w to the digraph.
|
|
* @param v the tail vertex
|
|
* @param w the head vertex
|
|
* @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("vertex " + v + " is not between 0 and " + (V-1));
|
|
if (w < 0 || w >= V) throw new IndexOutOfBoundsException("vertex " + w + " is not between 0 and " + (V-1));
|
|
adj[v].add(w);
|
|
E++;
|
|
}
|
|
|
|
/**
|
|
* Returns the vertices adjacent from vertex v in the digraph.
|
|
* @return the vertices adjacent from vertex v in the digraph, as an Iterable
|
|
* @param v the vertex
|
|
* @throws java.lang.IndexOutOfBoundsException unless 0 <= v < V
|
|
*/
|
|
public Iterable<Integer> adj(int v) {
|
|
if (v < 0 || v >= V) throw new IndexOutOfBoundsException();
|
|
return adj[v];
|
|
}
|
|
|
|
/**
|
|
* Returns the reverse of the digraph.
|
|
* @return the reverse of the digraph
|
|
*/
|
|
public Digraph reverse() {
|
|
Digraph R = new Digraph(V);
|
|
for (int v = 0; v < V; v++) {
|
|
for (int w : adj(v)) {
|
|
R.addEdge(w, v);
|
|
}
|
|
}
|
|
return R;
|
|
}
|
|
|
|
/**
|
|
* Returns a string representation of the graph.
|
|
* This method takes time proportional to E + V .
|
|
* @return the number of vertices V , followed by the number of edges E ,
|
|
* followed by the V adjacency lists
|
|
*/
|
|
@Override
|
|
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(String.format("%d: ", v));
|
|
for (int w : adj[v]) {
|
|
s.append(String.format("%d ", w));
|
|
}
|
|
s.append(NEWLINE);
|
|
}
|
|
return s.toString();
|
|
}
|
|
|
|
/**
|
|
* Unit tests the Digraph data type.
|
|
*/
|
|
public static void main(String[] args) {
|
|
In in = new In(args[0]);
|
|
Digraph G = new Digraph(in);
|
|
StdOut.println(G);
|
|
}
|
|
|
|
}
|