Question

我创建了一个程序来解决一个读取文本文件输入的迷宫。我设法使用深度优先搜索来解决它，结果在这样的小迷宫上很好：

一切都很好解决了中小型迷宫，但当迷宫变大时，它会给我一个ArrayIndexOutOfBoundsException错误（见下文）。

Enter maze file: test2.txt
Enter start node: 0
Enter goal node: 1
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 207
    at MazeGraph.addArc(MazeGraph.java:95)
    at MazeGraph.<init>(MazeGraph.java:51)
    at MazeSystem.<init>(MazeSystem.java:25)
    at MazeSystem.main(MazeSystem.java:37)
Java Result: 1

我的程序应该自动读取test2.txt（这是大型迷宫文件）文件中有多少个节点，但是会发生此错误。代码如下所示：

MazeGraph.java

import java.io.*;
import static java.lang.System.out;
import java.util.*;

/**
 * This class creates a representation of Maze as a Graph by reading from a text
 * file.
 *
 * @author Muhammad
 */
public class MazeGraph {

    final int node; //For declaring constant value of a node.
    int arc;
    List<Integer>[] adjacencyList;
    static Set<Integer> setOfNodes = new HashSet<>();
    private static Scanner scanNodeSize;

    /**
     * This constructors takes an integer parameter for reading node indexes in
     * a list of adjacent nodes.
     *
     * @param node - integer parameter for passing the nodes value from the file
     * and create a list of adjacent nodes.
     */
    MazeGraph(int node) {
        this.node = node;
        this.arc = 0;//initialise to empty arcs
        adjacencyList = (List<Integer>[]) new List[node];
        for (int index = 0; index < node; index++) {
            adjacencyList[index] = new LinkedList<Integer>();
        }
    }

    /**
     * The main constructor that takes a String parameter for reading maze file.
     *
     * @param mazeFile
     */
    public MazeGraph(String mazeFile) {
        this(getNodeSize(mazeFile));
        Scanner scan;
        try {
            //Scan maze file.
            scan = new Scanner(new File(mazeFile));
            /*loop when it has next integer then read two nodes from the file and add arc for it.*/
            while (scan.hasNextInt()) {
                int node1 = scan.nextInt();
                int node2 = scan.nextInt();
                addArc(node1, node2);
            }
        } catch (FileNotFoundException ex) {
            out.println(ex.getMessage());
        }
    }

    /**
     * This method returns a size of the set of nodes by taking a String
     * parameter which the name of the maze file.
     *
     * @param mazeFile - String parameter for reading maze file for scanning the
     * size of the nodes.
     * @return - returns an integer value for the size of the set of nodes.
     */
    public static int getNodeSize(String mazeFile) {

        try {
            scanNodeSize = new Scanner(new File(mazeFile));
            while (scanNodeSize.hasNextInt()) {
                int node1 = scanNodeSize.nextInt();
                int node2 = scanNodeSize.nextInt();
                setOfNodes.add(node1);
                setOfNodes.add(node2);
            }
            return setOfNodes.size();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        return setOfNodes.size();

    }

    /**
     * This method adds an arc by adding two different nodes in array of list
     * called adjacency list.
     *
     * @param node1 - first node.
     * @param node2 - next node.
     */
    private void addArc(int node1, int node2) {
        arc++; //Increase arc by one whenever this addArc method is called.
        adjacencyList[node1].add(node2);
        adjacencyList[node2].add(node1);

    }

    //Print the nodes and its arcs by looping through the adjacency list.
    public void print() {
        out.println(node + " Nodes, " + arc + " Arcs \n");
        for (int fromNode = 0; fromNode < node; fromNode++) {
            out.print(fromNode + " connected to ");
            for (int arcNode : adjacencyList[fromNode]) {
                out.print(arcNode + " ");
            }
            out.println();
        }
    }

    /**
     * This method returns a list of nodes to allow objects to be the target for
     * "for-each" statement in order to iterate through the nodes.
     *
     * @param nodes - an Integer parameter for getting the number of nodes in a
     * list.
     * @return - returns a list of nodes.
     */
    public Iterable<Integer> getAdjacencyList(int nodes) {
        return adjacencyList[nodes];
    }
}

在MazeGraph.java中，getNodeSize方法返回一个用于构造函数参数的整数。为了使它工作，我必须在构造函数的参数中取出getNodeSize方法，而是将一些更大的值放在那里，例如300。在堆栈跟踪中，它说问题出在addArc方法中。我试图找出如何解决这个问题，如果它已经在其他迷宫中工作，以便它也自动读入大型迷宫。如果有人能解决这个问题，我将不胜感激。

这是一个大文件。

Answer 1

好的，问题出在getNodeSize(String)。您返回setOfNodes.size()。问题是如果一个节点是单例（即它没有连接弧），那么它将不会列在迷宫文件中。例如，假设你的迷宫文件是＆＃34; 9999 1＆＃34;，没有别的。然后你的getNodeSize()方法将返回2.你的代码然后将节点数组实例化为大小2.然后你尝试在9999和1之间添加一个弧，但是接收ArrayIndexOutOfBoundsException因为那里有/** * This method returns a size of the set of nodes by taking a String * parameter which the name of the maze file. * * @param mazeFile - String parameter for reading maze file for scanning the * size of the nodes. * @return - returns an integer value for the size of the set of nodes. * @throws FileNotFoundException if the mazeFile could not be found */ public static int getNodeSize(String mazeFile) throws FileNotFoundException{ scanNodeSize = new Scanner(new File(mazeFile)); while (scanNodeSize.hasNextInt()) { int node1 = scanNodeSize.nextInt(); int node2 = scanNodeSize.nextInt(); setOfNodes.add(node1); setOfNodes.add(node2); } //Changes begin here Integer max = setOfNodes.stream().reduce(Integer::max).get(); return max+1; //Changes end here }数组中只有两个位置，但您尝试索引位置9999。

相反，您应该返回观察到的最大节点Id加1。以下代码实现了这一点：

Collection

注意：我删除了try-catch块并将其替换为throws声明。

更好的方法：混合数组和HashMap通常不赞成。使用HashMap<Integer,List<Integer>> adjacencyList = new HashMap<>();：

可能更好

adjacencyList.get(nodeId)

您可以通过调用public MazeGraph(String mazeFile) { adjacencyMap = new HashMap<>(); Scanner scan; try { //Scan maze file. scan = new Scanner(new File(mazeFile)); /*loop when it has next integer then read two nodes from the file and add arc for it.*/ while (scan.hasNextInt()) { int node1 = scan.nextInt(); int node2 = scan.nextInt(); List<Integer> node1AdjList = adjacencyMap.getOrDefault(node1,new LinkedList<Integer>()); List<Integer> node2AdjList = adjacencyMap.getOrDefault(node2,new LinkedList<Integer>()); node1AdjList.add(node2); node2AdjList.add(node1); adjacencyMap.put(node1, node1AdjList); adjacencyMap.put(node2, node2AdjList); } } catch (FileNotFoundException ex) { out.println(ex.getMessage()); } node = adjacencyMap.keySet().parallelStream().reduce(Integer::max).get(); }来访问任何节点的邻接列表，并且您的构造函数可以更改为：

$ch = curl_init(REQUEST_URL.$list.'/members/');

  curl_setopt($ch, CURLOPT_USERPWD, 'user:' . API_KEY);
  curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch, CURLOPT_TIMEOUT, 10);
  curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'GET');
  curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);

  $result = curl_exec($ch);
  $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
  $error = curl_error ( $ch );
  curl_close($ch);

ArrayIndexOutOfBoundsException用于生成具有深度优先搜索的迷宫图

1 个答案: