二叉树的实现

一个很简练的二叉树实现的例子，并能够对其进行前、中、后序的遍历！

package test;

public class Tree {  
   
    private int data;// 数据节点   
    private Tree left;// 左子树   
    private Tree right;// 右子树   
  
    public Tree(int data) {   
        this.data = data;   
        this.left = null;   
        this.right = null;   
    }   
  
    /**  
     * 创建二叉树，返回根结点  
     *   
     * @param input  
     * @return  
     */  
    public static Tree createTree(int[] input){   
        Tree root = null;   
        Tree temp = null;   
        for (int i = 0; i < input.length; i++){   
            // 创建根节点   
            if (root == null){   
                root = temp = new Tree(input[i]);   
            } else {   
                // 回到根结点   
                temp = root;   
                // 添加节点   
                while (temp.data != input[i]){   
                    if (input[i] <= temp.data){   
                        if (temp.left != null){   
                            temp = temp.left;   
                        } 
                        else{   
                            temp.left = new Tree(input[i]);   
                        }   
                    }
                    else{   
                        if(temp.right != null){   
                            temp = temp.right;   
                        } 
                        else{   
                            temp.right = new Tree(input[i]);   
                        }   
                    }   
                }   
            }   
        }   
        return root;   
    }   
  
    //tree的大小
    public  static int size(Tree tree){
    	if(tree==null)
    		return 0;
    	else
    		return size(tree.left)+size(tree.right)+1;
    }
    
    public static boolean isEmpty(Tree tree){
    	return size(tree)==0;
    }
    
    //tree的高度
    public static int height(Tree tree){
    	if(tree==null)
    		return 0;
    	else{
    		int lh=height(tree.left);
    		int rh=height(tree.right);
    		return 1+(lh>rh?lh:rh);
    	}
    } 
    
    /**  
     * 前序遍历  
     *   
     * @param tree  
     */  
    public static void preOrder(Tree tree) {   
        if (tree != null) {   
            System.out.print(tree.data + " ");   
            preOrder(tree.left);   
            preOrder(tree.right);   
        }   
    }   
  
    /**  
     * 中序遍历  
     *   
     * @param tree  
     */  
    public static void midOrder(Tree tree) {   
        if (tree != null) {   
            midOrder(tree.left);   
            System.out.print(tree.data + " ");   
            midOrder(tree.right);   
        }   
    }   
  
    /**  
     * 后序遍历  
     *   
     * @param tree  
     */ 
   
   public static void posOrder(Tree tree) {   
        if (tree != null) {   
            posOrder(tree.left);   
            posOrder(tree.right);   
            System.out.print(tree.data + " ");   
        }   
    }   
  
    /**  
     * @param args  
     */  
    public static void main(String[] args) {   
        int[] input = { 4, 2, 6, 1, 3, 5, 7 ,8};   
        Tree tree = createTree(input);
        System.out.println(isEmpty(tree));
        System.out.println(size(tree));
        System.out.println(height(tree));
        System.out.print("前序遍历：");//先访问根节点，再访问左子树，
        							  //最后访问右子树，前，中，后是对于根节点而言的 
        preOrder(tree);   
//      System.out.print("\n中序遍历：");   
//      midOrder(tree);   
//      System.out.print("\n后序遍历：");   
//      posOrder(tree);   
    }   
}