Question

我在拓扑排序方面遇到了一些问题。它可以找到lops，但它会计算一些任务（或者如果你想调用它的“节点”）几次。我认为这个问题与我的阅读方式或Edge类有关，但我无法看到它出错的地方。任何帮助将非常感激：）

enter code here
import java.util.*;
import java.io.*;
import java.lang.*;

class Task {

    int id, time, staff;
    int depA, depB;
    String name;
    int eStart, lStart;
    Edge outEdge;
    int cntPredecessors;
    boolean visited;

    Task(int id, String name, int time, int staff)  {
    this.id = id;
    this.name = name;
    this.time = time;
    this.staff = staff;
    visited = false;
    }

    public String getName() {
    return name;
    }
    public String toString() {
    return name;
    }
}

class Edge {
    Task id, name, time, staff;
    Edge neste;
    Task fra, til;

    Edge(Task id) {
    this.id = id;
        }
}



class Input {

    public static void main(String[] args) {

    if (args.length == 0) {
        System.out.println("enter a filename!");
        System.exit(1);
    } else if (args.length == 1) {
        String fil = args[0]+".txt";
        LesFraFil(fil);
        //  skrivUt();
        topSort();
    } else {
        System.out.println("too many parameters, try again...");
    }
    }

    static int antTask;
    static Task[] ids;
    static int tTid;
    static void LesFraFil(String fil) {

    int i = 0;
    int j;
    try {

        String lest;

        Scanner in = new Scanner(new FileReader(fil));
        Edge til;

        int counter = 0;
        antTask = in.nextInt();
        ids = new Task[antTask];
        System.out.println(antTask);
        while (in.hasNextLine()) {

        lest = in.nextLine();
        // hvis tom linje, så hopper den over
        if(lest.trim().length() == 0) continue;

        String split[] = lest.split("\\s+");
        int id = Integer.parseInt(split[0]);
        String act = split[1];
        int tid = Integer.parseInt(split[2]);
        int staff = Integer.parseInt(split[3]);
        int depA = Integer.parseInt(split[4]);
        tTid += tid;
        ids[i] = new Task(id, act, tid, staff);
        j = 4;

        /*
         * Lesingen av inputen skal avbrytes når den leser 0.
         * j er den som holder på hvor langt vi er i split arrayet
         * når den møter på 0 
         */
        while(split[j].compareTo("0") != 0) {
            int tmp = Integer.parseInt(split[j])-1;

            //  System.out.println(tmp+1 + " Aktivitetens navn : " + act); //+ " tiden aktiviteten tar tid: " + tid + " avhengihet: " + split[j]);

            j++;

            if (ids[tmp] == null) {
            ids[tmp] = new Task(id, act, tid, staff);
            ids[tmp].visited = true;
            }
            ids[i].cntPredecessors++;
            if(ids[tmp].outEdge == null) {
            ids[tmp].outEdge = new Edge(ids[i]);
            } else {
            til = ids[tmp].outEdge;

            while(til.neste != null) {
                til = til.neste;
            }
            til.neste = new Edge(ids[i]);
            }
        }
        counter++;
        i++;
        }

        if (antTask == counter) {
        System.out.println("Lesinga gikk som planlagt av fil: " + fil);
        System.out.println("Total arbeidstid: " + tTid);// + antTask + " == " + counter );
        } else {
        System.out.println("Noe gikk galt avslutter!");
        System.out.println(antTask + " || " + counter);
        System.exit(2);
        }
        in.close();
    } catch (Exception e) {
        System.err.println("ERROR!" + e.getMessage());
    }
    }


     static void skrivUt() {
    for (Task sort : ids) {
        System.out.print(sort.id + " " + sort.name);
        Edge til = sort.outEdge;
        while (til != null) {
        System.out.print(" " + til.id.id);
        til = til.neste;
        }
        System.out.println();
    }
   }

    static void topSort() {
    LinkedList<Task> list = new LinkedList<Task>();
    ArrayList<Task> array = new ArrayList<Task>();
    Task temp;
    int count = 0;
    int totalTime = 0;

    // Legger taskene i lista
        for (Task t : ids) {
        if(t.cntPredecessors == 0) {
        list.add(t);
        totalTime += t.time;
        //  System.out.println(t);
        t.visited = true;
        }   
    }
    for (Task t : ids) {
        if(t.cntPredecessors == 1) {

        list.add(t);
        totalTime += t.time;
        //  System.out.println(t);
        t.visited = true;
        }
    }

    // går i evig løkke til lista er tom.
    while (!list.isEmpty()) {
        temp = list.pop(); // fjerner elementet fra lista
        array.add(temp); // legger inn i arraylisten
        count++;
        //    System.out.println(temp);
        for(Edge til = temp.outEdge; til!=null;til=til.neste) {
        til.id.cntPredecessors--;
        if(til.id.cntPredecessors==0) {
            list.add(til.id);
        }
        }
    }
    if(count < antTask) {
        System.out.println("A loop has been found. Terminating...");
        System.exit(0);
    }
    System.out.println("Topological sort: " + Arrays.toString(array.toArray()));// den sorterte "arraylisten" 
    System.out.println("Total time spend: " + totalTime);
    }

} // End class Input

以下是输入文件的示例

8

1   Build-walls     4 2       5       0
2   Build-roofs     6 4       1       0
3   Put-on-wallpapers   1 2       1       2       0
4   Put-on-tiles        1 3       2       0
5   Build-foundation    4 2       0
6   Make-floor          2 2       5       0
7   Put-carpet-floor    4 2       6       2       0
8   Move-in         4 4       3       7       0

Answer 1

问题在于这个循环（在topSort()内）：

for (Task t : ids) {
    if(t.cntPredecessors == 1) {

    list.add(t);
    totalTime += t.time;
    //  System.out.println(t);
    t.visited = true;
    }
}

您只需将其删除即可。

原因：此循环添加到具有1个传入边缘的list个节点。稍后（在while循环中），对于这些节点，cntPredecessors字段可能会减少到0，这将使它们被推回到list，从而计算两次。< / p>

将来，请尝试将代码缩小到包含较少“噪音”的内容，即：用于说明问题的小集（或接近最小）代码。这将有助于减少对潜在回答者的理解（更不用说它可以帮助您自己看到问题）。

排序java的拓扑图

1 个答案: