【数据结构】Java实现二叉树遍历（递归）

递归实现遍历求节点数求数的深度十分简单，代码通俗易懂，但是递归来遍历的时候会产生大量的副本，在遍历一棵节点较多的树的时候，使用这种方法资源利用率不会很高

package DataStructure;

public class BinaryTreeTest {  

   private Node root;

   class Node{
       int data;
       Node left;
       Node right;
       public Node(int data){
           this.data = data;
           this.left = null;
           this.right= null;
       }
   }
   //构建一棵二叉树
   public BinaryTreeTest(){
       root = null;
   }
   //二叉树添加节点
   public void buildTree(Node node,int data){
       if(root == null){
           root = new Node(data);
       }else{
           if(data>node.data){
               if(node.right==null){
                   node.right=new Node(data);
               }else{
                   buildTree(node.right,data);
               }
           }else{
               if(node.left==null){
                   node.left=new Node(data);
               }else{
                   buildTree(node.left,data);
               }
           }
       }
   }
   //递归先序遍历
   public void preOrder(Node node){
       if(node != null){  
       System.out.print(node.data+" ");
       preOrder(node.left);
       preOrder(node.right);
       }
   }
   //递归中序遍历
   public void inOrder(Node node){
       if(node != null){
           inOrder(node.left);
           System.out.print(node.data+" ");
           inOrder(node.right);
       }
   }
   //递归后序遍历
   public void postOrder(Node node){
       if(node != null){
           postOrder(node.left);
           postOrder(node.right);
           System.out.print(node.data+" ");
           }
   }
   //递归树的深度
   public int high(Node node){
       if(node == null){
           return 0;
       }else{
       int i = high(node.left);
       int j = high(node.right);
       return i>j?i+1:j+1;
       }
   }
   //
   public int size(Node node){
       if(node == null){
           return 0;
       }else{
           int i = size(node.right);
           int j = size(node.left);
           return i+j+1;
       }
   }

   public static void main(String[] args){
       int a[]={62,88,58,47,35,73,51,99,37,93};
       BinaryTreeTest bt = new BinaryTreeTest();
       for(int i=0;i<a.length;i++){
           bt.buildTree(bt.root, a[i]);
       }
       System.out.println("先序遍历结果：");
       bt.preOrder(bt.root);
       System.out.println();
       System.out.println("中序遍历结果：");
       bt.inOrder(bt.root);
       System.out.println();
       System.out.println("后序遍历结果：");
       bt.postOrder(bt.root);
       System.out.println();
       System.out.println("二叉树的深度为："+bt.high(bt.root));
       System.out.println("二叉树的节点为："+bt.size(bt.root));
   }

}  

运行结果：