jgrapht：添加顶点和边后的动态图形错误

Question

希望你过得很好！我正在尝试编写一个程序，在那里我需要创建一个动态加权图，并获得从一个顶点到另一个顶点的最短路径。但运行程序后,我得到了以下异常：

run:
TEST1
TEST Vertex Add
Exception in thread "main" java.lang.IllegalArgumentException: no such vertex in graph: 1
at org.jgrapht.graph.AbstractGraph.assertVertexExist(AbstractGraph.java:132)
at org.jgrapht.graph.AbstractBaseGraph.addEdge(AbstractBaseGraph.java:141)
at dijkstra.Dijkstra.main(Dijkstra.java:26)
C:\Users\Lucas\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1
BUILD FAILED (total time: 0 seconds)

代码如下：

    import org.jgrapht.*;
    import org.jgrapht.alg.*;
    import org.jgrapht.graph.*;
    import java.util.List;
    import java.util.concurrent.ThreadLocalRandom;
    import org.jgrapht.alg.shortestpath.DijkstraShortestPath;

    public class Dijkstra {
public static void main(String args[]) {

    SimpleWeightedGraph<String, DefaultWeightedEdge>  graph = new SimpleWeightedGraph<String, DefaultWeightedEdge>(DefaultWeightedEdge.class);

    int i = generateNumberByRange(1,5);

     System.out.println("TEST1");
    for(int j=0; j<i; j++){

      graph.addVertex(String.valueOf(j));
      System.out.println("TEST Vertex Add");

    }
    for(int j=0;j<i;j++){

      DefaultWeightedEdge e1 = graph.addEdge(String.valueOf(j),String.valueOf(j+1)); 
      graph.setEdgeWeight(e1, generateNumberByRange(10,20));
      System.out.println(graph.getEdgeWeight(e1));
    }

    System.out.println("TEST2");
      graph.addVertex(String.valueOf(i));
      DefaultWeightedEdge e = graph.addEdge("0","1"); 
      graph.setEdgeWeight(e, generateNumberByRange(10,20)); 


    System.out.println("TEST3");

    System.out.println("Shortest path from START to END:");
    //List shortest_path =   DijkstraShortestPath.findPathBetween(graph,"0",String.valueOf(i));
    List shortest_path;
    //shortest_path = DijkstraShortestPath.findPathBetween(graph, "0","2");
    //System.out.println(shortest_path);

}

     public static int generateNumberByRange(int START, int END){
     return ThreadLocalRandom.current().nextInt(START, END + 1);
      }
      }

Answer 1

实际上，您需要修改此循环：

for(int j=0;j<i;j++){

      DefaultWeightedEdge e1 = graph.addEdge(String.valueOf(j),String.valueOf(j+1)); 
      graph.setEdgeWeight(e1, generateNumberByRange(10,20));
      System.out.println(graph.getEdgeWeight(e1));
    }

至

for(int j=0;j<i-1;j++){

      DefaultWeightedEdge e1 = graph.addEdge(String.valueOf(j),String.valueOf(j+1)); 
      graph.setEdgeWeight(e1, generateNumberByRange(10,20));
      System.out.println(graph.getEdgeWeight(e1));
    }

因为在循环的末尾，你试图得到一个顶点，它有这个索引i+1`，而这个索引并不存在。

希望有帮助