229 lines
8.0 KiB
Java
229 lines
8.0 KiB
Java
|
|
|
|
import edu.princeton.cs.introcs.In;
|
|
import edu.princeton.cs.introcs.StdOut;
|
|
|
|
/*************************************************************************
|
|
* Compilation: javac EdgeWeightedGraph.java
|
|
* Execution: java EdgeWeightedGraph filename.txt
|
|
* Dependencies: Bag.java Edge.java In.java StdOut.java
|
|
* Data files: http://algs4.cs.princeton.edu/43mst/tinyEWG.txt
|
|
*
|
|
* An edge-weighted undirected graph, implemented using adjacency lists.
|
|
* Parallel edges and self-loops are permitted.
|
|
*
|
|
* % java EdgeWeightedGraph tinyEWG.txt
|
|
* 8 16
|
|
* 0: 6-0 0.58000 0-2 0.26000 0-4 0.38000 0-7 0.16000
|
|
* 1: 1-3 0.29000 1-2 0.36000 1-7 0.19000 1-5 0.32000
|
|
* 2: 6-2 0.40000 2-7 0.34000 1-2 0.36000 0-2 0.26000 2-3 0.17000
|
|
* 3: 3-6 0.52000 1-3 0.29000 2-3 0.17000
|
|
* 4: 6-4 0.93000 0-4 0.38000 4-7 0.37000 4-5 0.35000
|
|
* 5: 1-5 0.32000 5-7 0.28000 4-5 0.35000
|
|
* 6: 6-4 0.93000 6-0 0.58000 3-6 0.52000 6-2 0.40000
|
|
* 7: 2-7 0.34000 1-7 0.19000 0-7 0.16000 5-7 0.28000 4-7 0.37000
|
|
*
|
|
*************************************************************************/
|
|
|
|
/**
|
|
* The EdgeWeightedGraph class represents an edge-weighted
|
|
* graph of vertices named 0 through V - 1, where each
|
|
* undirected edge is of type {@link Edge} and has a real-valued weight.
|
|
* It supports the following two primary operations: add an edge to the graph,
|
|
* iterate over all of the edges incident to a 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 to a given vertex, which takes
|
|
* time proportional to the number of such edges.
|
|
*
|
|
* For additional documentation,
|
|
* see <a href="http://algs4.cs.princeton.edu/43mst">Section 4.3</a> of
|
|
* Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
|
|
*
|
|
* @author Robert Sedgewick
|
|
* @author Kevin Wayne
|
|
*/
|
|
public class EdgeWeightedGraph {
|
|
private final int V;
|
|
private int E;
|
|
private Bag<Edge>[] adj;
|
|
|
|
/**
|
|
* Initializes an empty edge-weighted graph with V vertices and 0 edges.
|
|
* param V the number of vertices
|
|
* @throws java.lang.IllegalArgumentException if V < 0
|
|
*/
|
|
public EdgeWeightedGraph(int V) {
|
|
if (V < 0) throw new IllegalArgumentException("Number of vertices must be nonnegative");
|
|
this.V = V;
|
|
this.E = 0;
|
|
adj = (Bag<Edge>[]) new Bag[V];
|
|
for (int v = 0; v < V; v++) {
|
|
adj[v] = new Bag<Edge>();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Initializes a random edge-weighted graph with V vertices and E edges.
|
|
* param V the number of vertices
|
|
* param E the number of edges
|
|
* @throws java.lang.IllegalArgumentException if V < 0
|
|
* @throws java.lang.IllegalArgumentException if E < 0
|
|
*/
|
|
public EdgeWeightedGraph(int V, int E) {
|
|
this(V);
|
|
if (E < 0) throw new IllegalArgumentException("Number of edges must be nonnegative");
|
|
for (int i = 0; i < E; i++) {
|
|
int v = (int) (Math.random() * V);
|
|
int w = (int) (Math.random() * V);
|
|
double weight = Math.round(100 * Math.random()) / 100.0;
|
|
Edge e = new Edge(v, w, weight);
|
|
addEdge(e);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Initializes an edge-weighted graph 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 and edge weights,
|
|
* 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 EdgeWeightedGraph(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();
|
|
double weight = in.readDouble();
|
|
Edge e = new Edge(v, w, weight);
|
|
addEdge(e);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Initializes a new edge-weighted graph that is a deep copy of G .
|
|
* @param G the edge-weighted graph to copy
|
|
*/
|
|
public EdgeWeightedGraph(EdgeWeightedGraph 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<Edge> reverse = new Stack<Edge>();
|
|
for (Edge e : G.adj[v]) {
|
|
reverse.push(e);
|
|
}
|
|
for (Edge e : reverse) {
|
|
adj[v].add(e);
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/**
|
|
* Returns the number of vertices in the edge-weighted graph.
|
|
* @return the number of vertices in the edge-weighted graph
|
|
*/
|
|
public int V() {
|
|
return V;
|
|
}
|
|
|
|
/**
|
|
* Returns the number of edges in the edge-weighted graph.
|
|
* @return the number of edges in the edge-weighted graph
|
|
*/
|
|
public int E() {
|
|
return E;
|
|
}
|
|
|
|
/**
|
|
* Adds the undirected edge e to the edge-weighted graph.
|
|
* @param e the edge
|
|
* @throws java.lang.IndexOutOfBoundsException unless both endpoints are between 0 and V-1
|
|
*/
|
|
public void addEdge(Edge e) {
|
|
int v = e.either();
|
|
int w = e.other(v);
|
|
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(e);
|
|
adj[w].add(e);
|
|
E++;
|
|
}
|
|
|
|
/**
|
|
* Returns the edges incident on vertex v .
|
|
* @return the edges incident on vertex v as an Iterable
|
|
* @param v the vertex
|
|
* @throws java.lang.IndexOutOfBoundsException unless 0 <= v < V
|
|
*/
|
|
public Iterable<Edge> adj(int v) {
|
|
if (v < 0 || v >= V) throw new IndexOutOfBoundsException("vertex " + v + " is not between 0 and " + (V-1));
|
|
return adj[v];
|
|
}
|
|
|
|
/**
|
|
* Returns all edges in the edge-weighted graph.
|
|
* To iterate over the edges in the edge-weighted graph, use foreach notation:
|
|
* for (Edge e : G.edges()) .
|
|
* @return all edges in the edge-weighted graph as an Iterable.
|
|
*/
|
|
public Iterable<Edge> edges() {
|
|
Bag<Edge> list = new Bag<Edge>();
|
|
for (int v = 0; v < V; v++) {
|
|
int selfLoops = 0;
|
|
for (Edge e : adj(v)) {
|
|
if (e.other(v) > v) {
|
|
list.add(e);
|
|
}
|
|
// only add one copy of each self loop (self loops will be consecutive)
|
|
else if (e.other(v) == v) {
|
|
if (selfLoops % 2 == 0) list.add(e);
|
|
selfLoops++;
|
|
}
|
|
}
|
|
}
|
|
return list;
|
|
}
|
|
|
|
/**
|
|
* Returns a string representation of the edge-weighted 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 of edges
|
|
*/
|
|
@Override
|
|
public String toString() {
|
|
String NEWLINE = System.getProperty("line.separator");
|
|
StringBuilder s = new StringBuilder();
|
|
s.append(V + " " + E + NEWLINE);
|
|
for (int v = 0; v < V; v++) {
|
|
s.append(v + ": ");
|
|
for (Edge e : adj[v]) {
|
|
s.append(e + " ");
|
|
}
|
|
s.append(NEWLINE);
|
|
}
|
|
return s.toString();
|
|
}
|
|
|
|
/**
|
|
* Unit tests the EdgeWeightedGraph data type.
|
|
*/
|
|
public static void main(String[] args) {
|
|
In in = new In(args[0]);
|
|
EdgeWeightedGraph G = new EdgeWeightedGraph(in);
|
|
StdOut.println(G);
|
|
}
|
|
|
|
}
|