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概述：

  最近要學習寫網路爬蟲，所以把圖的深度和廣度搜索都再溫習一下。

圖結構展示：

實現過程：

首先，我們來看看圖結構在程式碼中的實現。有三塊邏輯：

1.圖中的節點：

public class GraphNode {
  public List<GraphEdge> edgeList = null;
 private String label = "";
 public GraphNode(String label) {
       this.label = label;
        if (edgeList == null) {
         edgeList = new ArrayList<GraphEdge>();
      }
   }
    /**
   * 給當前節點新增一條邊
  * GraphNode
   * @param
 
 edge
    *          新增的邊
   */
  public void addEdgeList(GraphEdge edge) {
       edgeList.add(edge);
 }
    public String getLabel() {
        return label;
 }
}

2.圖中的邊：

public class GraphEdge {
  private GraphNode nodeLeft;
 private GraphNode nodeRight;
   /**
    * @param nodeLeft
     *          邊的左端
   * @param
 
 nodeRight
   *          邊的右端
   */
  public GraphEdge(GraphNode nodeLeft, GraphNode nodeRight) {
       this.nodeLeft = nodeLeft;
     this.nodeRight = nodeRight;
   }
  public GraphNode getNodeLeft() {
      return nodeLeft;
  }
  public GraphNode getNodeRight() {
     return nodeRight;
 }
}

3.把節點和邊組合成一個圖結構：

public class MyGraph {
    private List<GraphNode> nodes = null;
 public void initGraph(int n) {
     if (nodes == null) {
         nodes = new ArrayList<GraphNode>();
      }
        GraphNode node = null;
        for (int i = 0; i < n; i++) {
           node = new GraphNode(String.valueOf(i));
          nodes.add(node);
        }
   }
    public void initGraph(int n, boolean b) {
       initGraph(n);
       GraphEdge edge01 = new GraphEdge(nodes.get(0), nodes.get(1));
       GraphEdge edge02 = new GraphEdge(nodes.get(0), nodes.get(2));
       GraphEdge edge13 = new GraphEdge(nodes.get(1), nodes.get(3));
       GraphEdge edge14 = new GraphEdge(nodes.get(1), nodes.get(4));
       GraphEdge edge25 = new GraphEdge(nodes.get(2), nodes.get(5));
       GraphEdge edge26 = new GraphEdge(nodes.get(2), nodes.get(6));
       GraphEdge edge37 = new GraphEdge(nodes.get(3), nodes.get(7));
       GraphEdge edge47 = new GraphEdge(nodes.get(4), nodes.get(7));
       GraphEdge edge56 = new GraphEdge(nodes.get(5), nodes.get(6));
        nodes.get(0).addEdgeList(edge01);
      nodes.get(0).addEdgeList(edge02);
      nodes.get(1).addEdgeList(edge13);
      nodes.get(1).addEdgeList(edge14);
      nodes.get(2).addEdgeList(edge25);
      nodes.get(2).addEdgeList(edge26);
      nodes.get(3).addEdgeList(edge37);
      nodes.get(4).addEdgeList(edge47);
      nodes.get(5).addEdgeList(edge56);
  }
    public void initGraph() {
       initGraph(8, false);
 }
    public List<GraphNode> getGraphNodes() {
        return nodes;
 }
}

深度優先搜尋：

public class DFSearch {
 /**
    * 深度遍歷
     * DFSearch
     * @param node
     *          當前節點
    * @param visited
  *          被訪問過的節點列表
  */
  public void searchTraversing(GraphNode node, List<GraphNode> visited) {
       // 判斷是否遍歷過
        if (visited.contains(node)) {
         return;
       }
        visited.add(node);
      System.out.println("節點：" + node.getLabel());
       for (int i = 0; i < node.edgeList.size(); i++) {
            searchTraversing(node.edgeList.get(i).getNodeRight(), visited);
     }
   }
}

廣度優先搜尋：

public class BFSearch {
 /**
    * 廣度優先搜尋
   * BFSearch
     * @param node
     *          搜尋的入口節點
     */
   public void searchTraversing(GraphNode node) {
      List<GraphNode> visited = new ArrayList<GraphNode>(); // 已經被訪問過的元素
      Queue<GraphNode> q = new LinkedList<GraphNode>(); // 用佇列存放依次要遍歷的元素
      q.offer(node);
        while (!q.isEmpty()) {
            GraphNode currNode = q.poll();
          if (!visited.contains(currNode)) {
                visited.add(currNode);
              System.out.println("節點：" + currNode.getLabel());
               for (int i = 0; i < currNode.edgeList.size(); i++) {
                    q.offer(currNode.edgeList.get(i).getNodeRight());
               }
           }
       }
   }
}

執行結果：

原始碼下載：

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