在我的App室内导航......在特定情况下....我必须找到从用户提供的特定来源到目的地的所有可能路径...... Algo工作正常，并提供所有可能的路径....但如何计算这些路径的距离.. ??? 这是工作算法......
class GraphFindAllPaths<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.
*/
public final Map<T, Map<T, Double>> graph = new HashMap<T, Map<T, Double>>();
/**
* Adds a new node to the graph. If the node already exists then its a
* no-op.
*
* @param node Adds to a graph. If node is null then this is a no-op.
* @return true if node is added, false otherwise.
*/
public boolean addNode(T node) {
if (node == null) {
throw new NullPointerException("The input node cannot be null.");
}
if (graph.containsKey(node)) return false;
graph.put(node, new HashMap<T, Double>());
return true;
}
/**
* Given the source and destination node it would add an arc from source
* to destination node. If an arc already exists then the value would be
* updated the new value.
*
* @param source the source node.
* @param destination the destination node.
* @param length if length if
* @throws NullPointerException if source or destination is null.
* @throws NoSuchElementException if either source of destination does not exists.
*/
public void addEdge (T source, T destination, double length) {
if (source == null || destination == null) {
throw new NullPointerException("Source and Destination, both should be non-null.");
}
if (!graph.containsKey(source) || !graph.containsKey(destination)) {
throw new NoSuchElementException("Source and Destination, both should be part of graph");
}
/* A node would always be added so no point returning true or false */
graph.get(source).put(destination, length);
}
/**
* Removes an edge from the graph.
*
* @param source If the source node.
* @param destination If the destination node.
* @throws NullPointerException if either source or destination specified is null
* @throws NoSuchElementException if graph does not contain either source or destination
*/
public void removeEdge (T source, T destination) {
if (source == null || destination == null) {
throw new NullPointerException("Source and Destination, both should be non-null.");
}
if (!graph.containsKey(source) || !graph.containsKey(destination)) {
throw new NoSuchElementException("Source and Destination, both should be part of graph");
}
graph.get(source).remove(destination);
}
/**
* Given a node, returns the edges going outward that node,
* as an immutable map.
*
* @param node The node whose edges should be queried.
* @return An immutable view of the edges leaving that node.
* @throws NullPointerException If input node is null.
* @throws NoSuchElementException If node is not in graph.
*/
public Map<T, Double> edgesFrom(T node) {
if (node == null) {
throw new NullPointerException("The node should not be null.");
}
Map<T, Double> edges = graph.get(node);
if (edges == null) {
throw new NoSuchElementException("Source node does not exist.");
}
return Collections.unmodifiableMap(edges);
}
/**
* Returns the iterator that travels the nodes of a graph.
*
* @return an iterator that travels the nodes of a graph.
*/
@Override public Iterator<T> iterator() {
//System.out.println(graph.keySet().iterator());
return graph.keySet().iterator();
}
}
/**
* Given a connected directed graph, find all paths between any two input points.
*/
public class FindAllPaths<T> {
private final GraphFindAllPaths<T> graph;
/**
* Takes in a graph. This graph should not be changed by the client
*/
public FindAllPaths(GraphFindAllPaths<T> graph) {
if (graph == null) {
throw new NullPointerException("The input graph cannot be null.");
}
this.graph = graph;
}
private void validate (T source, T destination) {
if (source == null) {
throw new NullPointerException("The source: " + source + " cannot be null.");
}
if (destination == null) {
throw new NullPointerException("The destination: " + destination + " cannot be null.");
}
if (source.equals(destination)) {
throw new IllegalArgumentException("The source and destination: " + source + " cannot be the same.");
}
}
/**
* Returns the list of paths, where path itself is a list of nodes.
*
* @param source the source node
* @param destination the destination node
* @return List of all paths
*/
public List<List<T>> getAllPaths(T source, T destination) {
validate(source, destination);
List<List<T>> paths = new ArrayList<List<T>>();
recursive(source, destination, paths, new LinkedHashSet<T>());
return paths;
}
// so far this dude ignore's cycles.
private void recursive (T current, T destination, List<List<T>> paths, LinkedHashSet<T> path) {
path.add(current);
if (current == destination) {
paths.add(new ArrayList<T>(path));
path.remove(current);
return;
}
final Set<T> edges = graph.edgesFrom(current).keySet();
for (T t : edges) {
if (!path.contains(t)) {
//System.out.println(t);
recursive (t, destination, paths, path);
}
}
path.remove(current);
}
public static void main(String[] args) {
GraphFindAllPaths<String> graphFindAllPaths = new GraphFindAllPaths<String>();
graphFindAllPaths.addNode("A");
graphFindAllPaths.addNode("B");
graphFindAllPaths.addNode("C");
graphFindAllPaths.addNode("D");
graphFindAllPaths.addEdge("A", "B", 10);
graphFindAllPaths.addEdge("A", "C", 15);
graphFindAllPaths.addEdge("B", "A", 10);
graphFindAllPaths.addEdge("C", "A", 15);
graphFindAllPaths.addEdge("B", "D", 10);
graphFindAllPaths.addEdge("C", "D", 20);
graphFindAllPaths.addEdge("D", "B", 10);
graphFindAllPaths.addEdge("D", "C", 20);
graphFindAllPaths.addEdge("B", "C", 5);
graphFindAllPaths.addEdge("C", "B", 5);
FindAllPaths<String> findAllPaths = new FindAllPaths<String>(graphFindAllPaths);
for (List<String> path :findAllPaths.getAllPaths("D", "A"))
{
System.out.println(path);
}
// assertEquals(paths, findAllPaths.getAllPaths("A", "D"));
}
}
代码打印所有可能的路径..
[D, B, A]
[D, B, C, A]
[D, C, A]
[D, C, B, A]
答案 0 :(得分：0)
我修改了Maryea提供的代码，以显示每条路径的总费用/距离。
package com.mini.test;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NoSuchElementException;
import java.util.Set;
class GraphFindAllPaths<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.
*/
public final Map<T, Map<T, Double>> graph = new HashMap<T, Map<T, Double>>();
/**
* Adds a new node to the graph. If the node already exists then its a
* no-op.
*
* @param node Adds to a graph. If node is null then this is a no-op.
* @return true if node is added, false otherwise.
*/
public boolean addNode(T node) {
if (node == null) {
throw new NullPointerException("The input node cannot be null.");
}
if (graph.containsKey(node)) return false;
graph.put(node, new HashMap<T, Double>());
return true;
}
/**
* Given the source and destination node it would add an arc from source
* to destination node. If an arc already exists then the value would be
* updated the new value.
*
* @param source the source node.
* @param destination the destination node.
* @param length if length if
* @throws NullPointerException if source or destination is null.
* @throws NoSuchElementException if either source of destination does not exists.
*/
public void addEdge (T source, T destination, double length) {
if (source == null || destination == null) {
throw new NullPointerException("Source and Destination, both should be non-null.");
}
if (!graph.containsKey(source) || !graph.containsKey(destination)) {
throw new NoSuchElementException("Source and Destination, both should be part of graph");
}
/* A node would always be added so no point returning true or false */
graph.get(source).put(destination, length);
}
/**
* Removes an edge from the graph.
*
* @param source If the source node.
* @param destination If the destination node.
* @throws NullPointerException if either source or destination specified is null
* @throws NoSuchElementException if graph does not contain either source or destination
*/
public void removeEdge (T source, T destination) {
if (source == null || destination == null) {
throw new NullPointerException("Source and Destination, both should be non-null.");
}
if (!graph.containsKey(source) || !graph.containsKey(destination)) {
throw new NoSuchElementException("Source and Destination, both should be part of graph");
}
graph.get(source).remove(destination);
}
/**
* Given a node, returns the edges going outward that node,
* as an immutable map.
*
* @param node The node whose edges should be queried.
* @return An immutable view of the edges leaving that node.
* @throws NullPointerException If input node is null.
* @throws NoSuchElementException If node is not in graph.
*/
public Map<T, Double> edgesFrom(T node) {
if (node == null) {
throw new NullPointerException("The node should not be null.");
}
Map<T, Double> edges = graph.get(node);
if (edges == null) {
throw new NoSuchElementException("Source node does not exist.");
}
return Collections.unmodifiableMap(edges);
}
/**
* Returns the iterator that travels the nodes of a graph.
*
* @return an iterator that travels the nodes of a graph.
*/
@Override public Iterator<T> iterator() {
//System.out.println(graph.keySet().iterator());
return graph.keySet().iterator();
}
}
/**
* Given a connected directed graph, find all paths between any two input points.
*/
public class FindAllPaths<T> {
private final GraphFindAllPaths<T> graph;
/**
* Takes in a graph. This graph should not be changed by the client
*/
public FindAllPaths(GraphFindAllPaths<T> graph) {
if (graph == null) {
throw new NullPointerException("The input graph cannot be null.");
}
this.graph = graph;
}
private void validate (T source, T destination) {
if (source == null) {
throw new NullPointerException("The source: " + source + " cannot be null.");
}
if (destination == null) {
throw new NullPointerException("The destination: " + destination + " cannot be null.");
}
if (source.equals(destination)) {
throw new IllegalArgumentException("The source and destination: " + source + " cannot be the same.");
}
}
/**
* Returns the list of paths, where path itself is a list of nodes.
*
* @param source the source node
* @param destination the destination node
* @return List of all paths
*/
public List<List<T>> getAllPaths(T source, T destination) {
validate(source, destination);
Map<List<T>,Double> pathWithCost = new HashMap<List<T>,Double>();
List<List<T>> paths = new ArrayList<List<T>>();
List<Double> totalCost = new ArrayList<Double>();
Double cost = new Double(0);
recursive(source, destination, paths, new LinkedHashSet<T>(),totalCost,cost, new HashMap<T, Double>());
for(int i=0;i<paths.size();i++){
pathWithCost.put(paths.get(i), totalCost.get(i));
}
return paths;
}
// so far this dude ignore's cycles.
private void recursive (T current, T destination, List<List<T>> paths, LinkedHashSet<T> path, List<Double> totalCost,Double cost, Map<T, Double> allEdges) {
path.add(current);
if(allEdges.get(current)!=null){
cost= cost+allEdges.get(current);
}
if (current == destination) {
cost= cost+allEdges.get(current);
paths.add(new ArrayList<T>(path));
cost= cost-allEdges.get(current);
totalCost.add(cost);
path.remove(current);
return;
}
allEdges = graph.edgesFrom(current);
final Set<T> edges = graph.edgesFrom(current).keySet();
for (T t : edges) {
if (!path.contains(t)) {
//System.out.println(t);
recursive (t, destination, paths, path,totalCost,cost , allEdges);
}
}
path.remove(current);
}
/**
* Returns the list of paths, where path itself is a list of nodes.
*
* @param source the source node
* @param destination the destination node
* @return List of all paths
*/
public Map<List<T>,Double> getAllPathsWithCost(T source, T destination) {
validate(source, destination);
Map<List<T>,Double> pathWithCost = new HashMap<List<T>,Double>();
List<List<T>> paths = new ArrayList<List<T>>();
List<Double> totalCost = new ArrayList<Double>();
Double cost = new Double(0);
recursiveWithCost(source, destination, paths, new LinkedHashSet<T>(),totalCost,cost, new HashMap<T, Double>());
for(int i=0;i<paths.size();i++){
pathWithCost.put(paths.get(i), totalCost.get(i));
}
return pathWithCost;
}
// so far this dude ignore's cycles.
private void recursiveWithCost (T current, T destination, List<List<T>> paths, LinkedHashSet<T> path, List<Double> totalCost,Double cost, Map<T, Double> allEdges) {
path.add(current);
if(allEdges.get(current)!=null){
cost= cost+allEdges.get(current);
}
if (current == destination) {
cost= cost+allEdges.get(current);
paths.add(new ArrayList<T>(path));
cost= cost-allEdges.get(current);
totalCost.add(cost);
path.remove(current);
return;
}
allEdges = graph.edgesFrom(current);
final Set<T> edges = graph.edgesFrom(current).keySet();
for (T t : edges) {
if (!path.contains(t)) {
//System.out.println(t);
recursiveWithCost (t, destination, paths, path,totalCost,cost , allEdges);
}
}
path.remove(current);
}
public static void main(String[] args) {
GraphFindAllPaths<String> graphFindAllPaths = new GraphFindAllPaths<String>();
graphFindAllPaths.addNode("A");
graphFindAllPaths.addNode("B");
graphFindAllPaths.addNode("C");
graphFindAllPaths.addNode("D");
graphFindAllPaths.addEdge("A", "B", 10);
graphFindAllPaths.addEdge("A", "C", 15);
graphFindAllPaths.addEdge("B", "A", 10);
graphFindAllPaths.addEdge("C", "A", 15);
graphFindAllPaths.addEdge("B", "D", 10);
graphFindAllPaths.addEdge("C", "D", 20);
graphFindAllPaths.addEdge("D", "B", 10);
graphFindAllPaths.addEdge("D", "C", 20);
graphFindAllPaths.addEdge("B", "C", 5);
graphFindAllPaths.addEdge("C", "B", 5);
FindAllPaths<String> findAllPaths = new FindAllPaths<String>(graphFindAllPaths);
System.out.println("All possible Paths : ");
for (List<String> path :findAllPaths.getAllPaths("D", "A"))
{
System.out.println(path);
}
System.out.println("\nAll possible paths with total distance : ");
Map<List<String>,Double> pathWithCost = findAllPaths.getAllPathsWithCost("D", "A");
for(Entry<List<String>, Double> s : pathWithCost.entrySet()){
System.out.println(s);
}
// assertEquals(paths, findAllPaths.getAllPaths("A", "D"));
}
}
答案 1 :(得分：-1)
了解每个链接的距离。对这些链接的距离求和。完成。