Java学习(十八)：二叉树的三种递归遍历

  1 public class StudentNode
  2 {
  3     private String name;
  4     
  5     private StudentNode leftNode;
  6     
  7     private StudentNode rightNode;
  8     
  9     public String getName()
 10     {
 11         return name;
 12     }
 13     
 14     public void setName(String name)
 15     {
 16         this.name = name;
 17     }
 18     
 19     public StudentNode getLeftNode()
 20     {
 21         return leftNode;
 22     }
 23     
 24     public void setLeftNode(StudentNode leftNode)
 25     {
 26         this.leftNode = leftNode;
 27     }
 28     
 29     public StudentNode getRightNode()
 30     {
 31         return rightNode;
 32     }
 33     
 34     public void setRightNode(StudentNode rightNode)
 35     {
 36         this.rightNode = rightNode;
 37     }
 38     
 39     public static void main(String[] args)
 40     {
 41         StudentNode root = new StudentNode();
 42         root.setName("Name1");
 43         StudentNode node2 = new StudentNode();
 44         node2.setName("Name2");
 45         StudentNode node3 = new StudentNode();
 46         node3.setName("Name3");
 47         StudentNode node4 = new StudentNode();
 48         node4.setName("Name4");
 49         StudentNode node5 = new StudentNode();
 50         node5.setName("Name5");
 51         StudentNode node6 = new StudentNode();
 52         node6.setName("Name6");
 53         StudentNode node7 = new StudentNode();
 54         node7.setName("Name7");
 55         //
 56         // ****root***
 57         // ***/ **\***
 58         // **2 ****5**
 59         // */ \ **/***
 60         // 3 *4 **6***
 61         // *******\***
 62         // ********7**
 63         //
 64         root.setLeftNode(node2);
 65         root.setRightNode(node5);
 66         node2.setLeftNode(node3);
 67         node2.setRightNode(node4);
 68         node5.setLeftNode(node6);
 69         node6.setRightNode(node7);
 70         
 71         // 前序遍历1-2-3-4-5-6-7
 72         rootFirst(root);
 73         // 中序遍历3-2-4-1-6-7-5
 74         rootMiddle(root);
 75         // 后序遍历3-4-2-7-6-5-1
 76         rootLast(root);
 77     }
 78     
 79     private static void rootFirst(StudentNode node)
 80     {
 81         System.out.println(node.getName());
 82         if (null != node.getLeftNode())
 83         {
 84             rootFirst(node.getLeftNode());
 85         }
 86         if (null != node.getRightNode())
 87         {
 88             rootFirst(node.getRightNode());
 89         }
 90     }
 91     
 92     private static void rootMiddle(StudentNode node)
 93     {
 94         if (null != node.getLeftNode())
 95         {
 96             rootMiddle(node.getLeftNode());
 97         }
 98         System.out.println(node.getName());
 99         if (null != node.getRightNode())
100         {
101             rootMiddle(node.getRightNode());
102         }
103     }
104     
105     private static void rootLast(StudentNode node)
106     {
107         if (null != node.getLeftNode())
108         {
109             rootLast(node.getLeftNode());
110         }
111         if (null != node.getRightNode())
112         {
113             rootLast(node.getRightNode());
114         }
115         System.out.println(node.getName());
116     }
117 }