我已经在 Java 中实现了两种算法，在测试深度优先搜索时，当有 12 个节点时，它似乎花费了令人难以置信的时间，当使用 A* 时，它在几秒钟内完成，我只是想知道这是否可以预期或难道我做错了什么？它现在在后台运行搜索，因为我输入了这个并且已经持续了几分钟。我通常不会介意，但我必须测试多达 500 个节点，以这种速度可能需要几天时间，这是我应该预料到的还是我做错了什么？
谢谢！
import java.util.*;
@SuppressWarnings({ "rawtypes", "unchecked" })
public class DepthFirstSearch {
Routes distances;
static Routes routes;
int firstNode;
String result = new String();
ArrayList firstRoute, bestRoute;
int nodes = 0;
int routeCost = 0;
int bestCost = Integer.MAX_VALUE;
public DepthFirstSearch(Routes matrix, int firstNode) { //new instance
distances = matrix;
this.firstNode = firstNode;
}
public void run () { //run algorithm
long startTime = System.nanoTime();
firstRoute = new ArrayList();
firstRoute.add(firstNode);
bestRoute = new ArrayList();
nodes++;
long endTime = System.nanoTime();
System.out.println("Depth First Search\n");
search(firstNode, firstRoute);
System.out.println(result);
System.out.println("Visited Nodes: "+nodes);
System.out.println("\nBest solution: "+bestRoute.toString() + "\nCost: "+bestCost);
System.out.println("\nElapsed Time: "+(endTime-startTime)+" ns\n");
}
/**
* @param from node where we start the search.
* @param route followed route for arriving to node "from".
*/
public void search (int from, ArrayList chosenRoute) {
// we've found a new solution
if (chosenRoute.size() == distances.getCitiesCount()) {
chosenRoute.add(firstNode);
nodes++;
// update the route's cost
routeCost += distances.getCost(from, firstNode);
if (routeCost < bestCost) {
bestCost = routeCost;
bestRoute = (ArrayList)chosenRoute.clone();
}
result += chosenRoute.toString() + " - Cost: "+routeCost + "\n";
// update the route's cost (back to the previous value)
routeCost -= distances.getCost(from, firstNode);
}
else {
for (int to=0; to<distances.getCitiesCount(); to++){
if (!chosenRoute.contains(to)) {
ArrayList increasedRoute = (ArrayList)chosenRoute.clone();
increasedRoute.add(to);
nodes++;
// update the route's cost
routeCost += distances.getCost(from, to);
search(to, increasedRoute);
// update the route's cost (back to the previous value)
routeCost -= distances.getCost(from, to);
}
}
}
}
}