Prerrequisito: Clase Genérica
También podemos usarlos para codificar Graph en Java . La clase Graph se implementa usando HashMap en Java . Como sabemos que HashMap contiene una clave y un valor, representamos los Nodes como claves y su lista de adyacencia en valores en el gráfico.
Ilustración: un gráfico no dirigido y no ponderado con 5 vértices.
La array de adyacencia es la siguiente:
La lista de adyacencia es la siguiente:
Acercarse:
Algo poco probable en C++, usamos <> para especificar tipos de parámetros en la creación de clases genéricas.
Sintaxis: Para crear objetos de una clase genérica
BaseType <Type> obj = new BaseType <Type>()
Nota: en el tipo de parámetro, no podemos usar primitivas como ‘int’, ‘char’ o ‘double’.
Ejemplo
Java
// Java program to implement Graph
// with the help of Generics
import java.util.*;
class Graph<T> {
// We use Hashmap to store the edges in the graph
private Map<T, List<T> > map = new HashMap<>();
// This function adds a new vertex to the graph
public void addVertex(T s)
{
map.put(s, new LinkedList<T>());
}
// This function adds the edge
// between source to destination
public void addEdge(T source,
T destination,
boolean bidirectional)
{
if (!map.containsKey(source))
addVertex(source);
if (!map.containsKey(destination))
addVertex(destination);
map.get(source).add(destination);
if (bidirectional == true) {
map.get(destination).add(source);
}
}
// This function gives the count of vertices
public void getVertexCount()
{
System.out.println("The graph has "
+ map.keySet().size()
+ " vertex");
}
// This function gives the count of edges
public void getEdgesCount(boolean bidirection)
{
int count = 0;
for (T v : map.keySet()) {
count += map.get(v).size();
}
if (bidirection == true) {
count = count / 2;
}
System.out.println("The graph has "
+ count
+ " edges.");
}
// This function gives whether
// a vertex is present or not.
public void hasVertex(T s)
{
if (map.containsKey(s)) {
System.out.println("The graph contains "
+ s + " as a vertex.");
}
else {
System.out.println("The graph does not contain "
+ s + " as a vertex.");
}
}
// This function gives whether an edge is present or not.
public void hasEdge(T s, T d)
{
if (map.get(s).contains(d)) {
System.out.println("The graph has an edge between "
+ s + " and " + d + ".");
}
else {
System.out.println("The graph has no edge between "
+ s + " and " + d + ".");
}
}
// Prints the adjancency list of each vertex.
@Override
public String toString()
{
StringBuilder builder = new StringBuilder();
for (T v : map.keySet()) {
builder.append(v.toString() + ": ");
for (T w : map.get(v)) {
builder.append(w.toString() + " ");
}
builder.append("\n");
}
return (builder.toString());
}
}
// Driver Code
public class Main {
public static void main(String args[])
{
// Object of graph is created.
Graph<Integer> g = new Graph<Integer>();
// edges are added.
// Since the graph is bidirectional,
// so boolean bidirectional is passed as true.
g.addEdge(0, 1, true);
g.addEdge(0, 4, true);
g.addEdge(1, 2, true);
g.addEdge(1, 3, true);
g.addEdge(1, 4, true);
g.addEdge(2, 3, true);
g.addEdge(3, 4, true);
// Printing the graph
System.out.println("Graph:\n"
+ g.toString());
// Gives the no of vertices in the graph.
g.getVertexCount();
// Gives the no of edges in the graph.
g.getEdgesCount(true);
// Tells whether the edge is present or not.
g.hasEdge(3, 4);
// Tells whether vertex is present or not
g.hasVertex(5);
}
}
Producción:
Graph: 0: 1 4 1: 0 2 3 4 2: 1 3 3: 1 2 4 4: 0 1 3 The graph has 5 vertex The graph has 7 edges. The graph has an edge between 3 and 4. The graph does not contain 5 as a vertex.