迭代通過定向的ArrayList的邊緣HashMap中，提取有向邊數據

Question

我試圖通過一個HashMap迭代包含有向邊的ArrayList，對於Edgeweighted向圖。我遵循了類似問題的說明，但無法正常工作。

我想： 迭代通過HashMap中，檢索每個ArrayList中。 然後迭代ArrayList中的directedEdges。 打印出來的有向邊，它具有以下toString方法：

public String toString(){ 
    return String.format("%s->%s %d", v, w, weight); 
    } 

低於滿EdgeDirectedGraph類，toString方法我查詢是在底部。

import java.util.*; 
import java.io.*; 
import java.util.logging.Level; 
import java.util.logging.Logger; 

public class EdgeWeightedDiGraph{ 
private static final String NEWLINE = System.getProperty("line.separator"); 
private int V; 
private int E; 
private HashMap<String, ArrayList<DirectedEdge>> adjacencyList; 

public EdgeWeightedDiGraph(String filename, String delim){ 
    BufferedReader br = null; 
     try{ 
     br = new BufferedReader(new FileReader(filename)); 
     E = 0; 
     V = Integer.parseInt(br.readLine()); 
     //System.out.println(V); 
     String line = null; 
     this.adjacencyList = new HashMap<String, ArrayList<DirectedEdge>>(); 
     while ((line = br.readLine()) != null) { 
      //adj = (Bag<Integer>[]) new Bag[V]; 
      String arr[] = line.split(delim); // properties 
      String v = arr[0]; 
      String w = arr[1]; 
      int e = Integer.parseInt(arr[2]); 
      DirectedEdge dEdge = new DirectedEdge(v, w, e); 
      addEdge(dEdge); 
      System.out.println(dEdge.from()+dEdge.to()+dEdge.weight()); 
      } 
      } 
     catch (FileNotFoundException ex) { 
      System.out.println("Error: File not found"); 
      Logger.getLogger(EdgeWeightedDiGraph.class.getName()).log(Level.SEVERE, null, ex); 
      }  
     catch (IOException ex) { 
      Logger.getLogger(EdgeWeightedDiGraph.class.getName()).log(Level.SEVERE, null, ex); 
      } 
     finally{ 
     try { 
      br.close(); 
     } 
     catch (IOException ex) { 
      Logger.getLogger(EdgeWeightedDiGraph.class.getName()).log(Level.SEVERE, null, ex); 
     } 
    } 

} 

    public HashMap getMap(){ 
     return adjacencyList; 
    } 

public int V(){ 
    return V; 
} 
public int E(){ 
    return E; 
} 
public void addEdge(DirectedEdge e) 
{ 
    String v = e.from(); 
    String w = e.to(); 
    ArrayList<DirectedEdge> item = new ArrayList<DirectedEdge>(); 
    item.add(e); 
    adjacencyList.put(v, item); 
    System.out.println(v+item); 
    E++; 
} 

public Iterable<DirectedEdge> adjacencyList(String v){ 
    return adjacencyList.get(v); 
} 

public Iterable<DirectedEdge> edges() 
{ 

public String toString() { 
     StringBuilder s = new StringBuilder(); 
     s.append(V + " " + E + NEWLINE); 
     for (HashMap.Entry<String, ArrayList<DirectedEdge>> entry : adjacencyList.entrySet()){ 
      ArrayList<DirectedEdge> arrList = entry.getValue(); 
      for(DirectedEdge e : arrList){ 
       s.append(e + " "); } 
      s.append(NEWLINE); 
     } 
     return s.toString(); 
    } 
} 

下面是輸出： 我可以看到，有向邊被添加到該圖中，但只有一半在toString（）方法打印出來。

Print out of edges being added 
A[A->B 5] 
AB5, 
B[B->C 4] 
BC4, 
C[C->D 8] 
CD8, 
D[D->C 8] 
DC8, 
D[D->E 6] 
DE6 , 
A[A->D 5] 
AD5, 
C[C->E 2] 
CE2, 
E[E->B 3] 
EB3, 
A[A->E 7] 
AE7 

「的toString（）輸出：A->電子7 B->的C 4 C-> e 2的D->電子6 E-> B 3」

Answer 1

的問題是你總是創建一個新的DirectedEdge列表，當您添加和邊緣，而不是使用現有的列表，如果它存在。

public void addEdge(DirectedEdge e) 
{ 
    String v = e.from(); 
    String w = e.to(); 

    // Check if there is already an edge array 
    ArrayList<DirectedEdge> item = adjacencyList.get(v); 
    if(item == null) { 
     // Does not exist, create it 
     item = new ArrayList<DirectedEdge>(); 
    } 
    item.add(e); 
    adjacencyList.put(v, item); 
    System.out.println(v+item); 
}