JGrapht：添加顶点和边后的动态图形错误

Question

希望你做得很好！ 我想编写一个程序，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。但在运行程序后，我得到这个异常：

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) 

这里是代码：

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

其实你需要修改这个循环：

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)); 
    } 

到

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)); 
    } 

因为在结束时循环尝试获取具有此索引i + 1`的顶点，该顶点不存在。

希望得到这个帮助