我正在开发一个Minecraft插件,在其中需要创建一个导航系统的图表。我进行了一些研究,并发现应该能够使用Dijkstra算法,但我遇到了一个问题。当寻找最短路径时,有时会出现无限循环的情况(并非总是如此,通常在前2-3次运行后才会进入循环)。
当玩家想要到达目的地时,我会搜索到最近的顶点,并使用该顶点作为参数运行computePaths。然后,当我运行getShortestPathTo时,有时会陷入无限循环中,而我会耗尽内存(这是有道理的,因为我正在将相同的顶点添加到列表中)。您能看出它为什么会卡住吗?据我所知,Dijkstra应该能够处理从A节点到B节点和从B节点到A节点对吧?
以下是我的代码:
当插件第一次启用时,我会从类似于以下内容的配置文件中加载所有顶点(这是我正在使用的测试文件): 在此添加顶点和边缘(不确定是否相关,但认为可能有帮助)。
当玩家想要到达目的地时,我会搜索到最近的顶点,并使用该顶点作为参数运行computePaths。然后,当我运行getShortestPathTo时,有时会陷入无限循环中,而我会耗尽内存(这是有道理的,因为我正在将相同的顶点添加到列表中)。您能看出它为什么会卡住吗?据我所知,Dijkstra应该能够处理从A节点到B节点和从B节点到A节点对吧?
以下是我的代码:
public class Dijkstra {
public static void computePaths(Vertex source) {
source.minDistance = 0.;
PriorityQueue<Vertex> vertexQueue = new PriorityQueue<Vertex>();
vertexQueue.add(source);
while (!vertexQueue.isEmpty()) {
Vertex u = vertexQueue.poll();
// Visit each edge exiting u
for (Edge e : u.adjacencies) {
Vertex v = e.target;
double weight = e.weight;
double distanceThroughU = u.minDistance + weight;
if (distanceThroughU < v.minDistance) {
vertexQueue.remove(v);
v.minDistance = distanceThroughU;
v.previous = u;
vertexQueue.add(v);
}
}
}
}
public static List<Vertex> getShortestPathTo(Vertex target) {
List<Vertex> path = new ArrayList<Vertex>();
for (Vertex vertex = target; vertex != null; vertex = vertex.previous) {
path.add(vertex);
}
Collections.reverse(path);
return path;
}
}
以及顶点类:
public class Vertex implements Comparable<Vertex>
{
public final String name;
public Edge[] adjacencies;
public double minDistance = Double.POSITIVE_INFINITY;
public Vertex previous;
public Location location;
public Vertex(String argName) { name = argName; }
public Vertex(String argName,Location l) { name = argName; location = l;}
public String toString() { return name; }
public int compareTo(Vertex other)
{
return Double.compare(minDistance, other.minDistance);
}
}
当插件第一次启用时,我会从类似于以下内容的配置文件中加载所有顶点(这是我正在使用的测试文件): 在此添加顶点和边缘(不确定是否相关,但认为可能有帮助)。
public void loadAllVertex() {
ConfigurationSection section = nodeConfig.config.getConfigurationSection("nodes");
for (String key: section.getKeys(false)) {
String locationString = nodeConfig.getString("nodes." + key + ".location");
if (locationString == null)
return;
String[] locationSplit = locationString.split(",");
if (locationSplit.length <=1) {
log.log(Level.SEVERE, "Location is not specified correctly in nodes.yml");
return;
}
Location l = new Location(Bukkit.getWorlds().get(0),Integer.parseInt(locationSplit[0]),Integer.parseInt(locationSplit[1]),Integer.parseInt(locationSplit[2]));
Vertex tmpVertex = new Vertex(key, l);
allNodes.add(tmpVertex);
}
for (Vertex v : allNodes) {
String path = "nodes." + v.name + ".connectedTo";
List<String> connectedTo = nodeConfig.getStringList(path,true);
List<Edge> edges = new ArrayList<>();
for (String sideNodeName : connectedTo) {
Vertex vertexCon = GraphUtils.getVertexByName(allNodes, sideNodeName);
if (vertexCon == null) {
log.warning("The '" + sideNodeName + "' node is not defined");
return;
}
//A.adjacencies = new Edge[]{ new Edge(M, 8) };
edges.add(new Edge(vertexCon,vertexCon.location.distance(v.location)));
}
Edge[] arrayEdges = new Edge[edges.size()];
arrayEdges = edges.toArray(arrayEdges);
v.adjacencies = arrayEdges;
}
}
while (!vertexQueue.isEmpty()) {
- cabreracanal