Estructuras_de_Datos/src/cl/cromer/estructuras/GrafoNoDirigido.java

package cl.cromer.estructuras;

import java.util.*;

/*****************************************************************************
 * File: UndirectedGraph.java
 * Author: Keith Schwarz (htiek@cs.stanford.edu)
 *
 * A class representing an undirected graph where each edge has an associated
 * real-valued length.  Internally, the class is represented by an adjacency
 * list where each edges appears twice - once in the forward direction and
 * once in the reverse.  In fact, this implementation was formed by taking
 * a standard adjacency list and then duplicating the logic to ensure each
 * edge appears twice.
 */
@SuppressWarnings({"unused", "unchecked"})
public final class GrafoNoDirigido<T> implements Iterable<T> {
	/* A map from nodes in the graph to sets of outgoing edges.  Each
	 * set of edges is represented by a map from edges to doubles.
	 */
	private final Map<T, Set<T>> mGraph = new HashMap<>();

	/**
	 * Adds a new node to the graph.  If the node already exists, this
	 * function is a no-op.
	 *
	 * @param node The node to add.
	 * @return Whether or not the node was added.
	 */
	public boolean addNode(T node) {
        /* If the node already exists, don't do anything. */
		if (mGraph.containsKey(node))
			return false;

        /* Otherwise, add the node with an empty set of outgoing edges. */
		mGraph.put(node, new HashSet<>());
		return true;
	}

	/**
	 * Remove a node from the graph.
	 *
	 * @param node The node to remove.
	 * @return Whether or not the node was removed.
	 */
	public boolean removeNode(T node) {
        /* If the node already exists, don't do anything. */
		if (!mGraph.containsKey(node))
			return false;

        /* Otherwise, remove the node. */
		mGraph.remove(node);
		return true;
	}

	/**
	 * Given a node, returns whether that node exists in the graph.
	 *
	 * @param node The node in question.
	 * @return Whether that node eixsts in the graph.
	 */
	public boolean nodeExists(T node) {
		return mGraph.containsKey(node);
	}

	/**
	 * Given two nodes, adds an arc of that length between those nodes.  If
	 * either endpoint does not exist in the graph, throws a
	 * NoSuchElementException.
	 *
	 * @param one The first node.
	 * @param two The second node.
	 * @throws NoSuchElementException If either the start or destination nodes
	 *                                do not exist.
	 */
	public void addEdge(T one, T two) {
        /* Confirm both endpoints exist. */
		if (!mGraph.containsKey(one) || !mGraph.containsKey(two))
			throw new NoSuchElementException("Both nodes must be in the graph.");

        /* Add the edge in both directions. */
		mGraph.get(one).add(two);
		mGraph.get(two).add(one);
	}

	/**
	 * Removes the edge between the indicated endpoints from the graph.  If the
	 * edge does not exist, this operation is a no-op.  If either endpoint does
	 * not exist, this throws a NoSuchElementException.
	 *
	 * @param one The start node.
	 * @param two The destination node.
	 * @throws NoSuchElementException If either node is not in the graph.
	 */
	public void removeEdge(T one, T two) {
        /* Confirm both endpoints exist. */
		if (!mGraph.containsKey(one) || !mGraph.containsKey(two))
			throw new NoSuchElementException("Both nodes must be in the graph.");

        /* Remove the edges from both adjacency lists. */
		mGraph.get(one).remove(two);
		mGraph.get(two).remove(one);
	}

	/**
	 * Given two endpoints, returns whether an edge exists between them.  If
	 * either endpoint does not exist in the graph, throws a
	 * NoSuchElementException.
	 *
	 * @param one The first endpoint.
	 * @param two The second endpoint.
	 * @return Whether an edge exists between the endpoints.
	 * @throws NoSuchElementException If the endpoints are not nodes in the
	 *                                graph.
	 */
	public boolean edgeExists(T one, T two) {
        /* Confirm both endpoints exist. */
		if (!mGraph.containsKey(one) || !mGraph.containsKey(two))
			throw new NoSuchElementException("Both nodes must be in the graph.");

        /* Graph is symmetric, so we can just check either endpoint. */
		return mGraph.get(one).contains(two);
	}

	/**
	 * Given a node in the graph, returns an immutable view of the edges
	 * leaving that node.
	 *
	 * @param node The node whose edges should be queried.
	 * @return An immutable view of the edges leaving that node.
	 * @throws NoSuchElementException If the node does not exist.
	 */
	public Set<T> edgesFrom(T node) {
        /* Check that the node exists. */
		Set<T> arcs = mGraph.get(node);
		if (arcs == null)
			throw new NoSuchElementException("Source node does not exist.");

		return Collections.unmodifiableSet(arcs);
	}

	/**
	 * Returns whether a given node is contained in the graph.
	 *
	 * @param node The node to test for inclusion.
	 * @return Whether that node is contained in the graph.
	 */
	public boolean containsNode(T node) {
		return mGraph.containsKey(node);
	}

	/**
	 * Returns an iterator that can traverse the nodes in the graph.
	 *
	 * @return An iterator that traverses the nodes in the graph.
	 */
	public Iterator<T> iterator() {
		return mGraph.keySet().iterator();
	}

	/**
	 * Returns the number of nodes in the graph.
	 *
	 * @return The number of nodes in the graph.
	 */
	public int size() {
		return mGraph.size();
	}

	/**
	 * Returns whether the graph is empty.
	 *
	 * @return Whether the graph is empty.
	 */
	public boolean isEmpty() {
		return mGraph.isEmpty();
	}

	/**
	 * Returns a human-readable representation of the graph.
	 *
	 * @return A human-readable representation of the graph.
	 */
	public String toString() {
		return mGraph.toString();
	}
}

class Node {
	private int value;

	public Node(int value) {
		this.value = value;
	}

	public int getValue() {
		return value;
	}

	public void setValue(int value) {
		this.value = value;
	}
}