二叉树基本操作演示程序 设计一个与二叉树基本操作相关的演示程序。 要求： （1）创建二叉树。按照用户需要的二叉树，构建二叉树。 （2）分别以先序、中序、后序三种遍历访问二叉树。 （3）输出二叉树的叶子结点及叶子结点的个数。 （4）输出二叉树的高度。

下面是一个基于Python的二叉树演示程序，实现了创建二叉树、遍历二叉树、输出叶子节点及个数、输出树高等功能：

class Node:
    def __init__(self, data):
        self.left = None
        self.right = None
        self.data = data

class BinaryTree:
    def __init__(self):
        self.root = None

    def insert(self, data):
        if self.root is None:
            self.root = Node(data)
        else:
            self._insert(data, self.root)

    def _insert(self, data, node):
        if data < node.data:
            if node.left is None:
                node.left = Node(data)
            else:
                self._insert(data, node.left)
        else:
            if node.right is None:
                node.right = Node(data)
            else:
                self._insert(data, node.right)

    def preorder_traversal(self, node):
        if node is not None:
            print(node.data, end=' ')
            self.preorder_traversal(node.left)
            self.preorder_traversal(node.right)

    def inorder_traversal(self, node):
        if node is not None:
            self.inorder_traversal(node.left)
            print(node.data, end=' ')
            self.inorder_traversal(node.right)

    def postorder_traversal(self, node):
        if node is not None:
            self.postorder_traversal(node.left)
            self.postorder_traversal(node.right)
            print(node.data, end=' ')

    def count_leaves(self, node):
        if node is None:
            return 0
        elif node.left is None and node.right is None:
            return 1
        else:
            return self.count_leaves(node.left) + self.count_leaves(node.right)

    def height(self, node):
        if node is None:
            return 0
        else:
            left_height = self.height(node.left)
            right_height = self.height(node.right)
            return max(left_height, right_height) + 1

# 创建二叉树
tree = BinaryTree()
tree.insert(50)
tree.insert(30)
tree.insert(20)
tree.insert(40)
tree.insert(70)
tree.insert(60)
tree.insert(80)

# 遍历二叉树
print("Preorder traversal:")
tree.preorder_traversal(tree.root)
print("\nInorder traversal:")
tree.inorder_traversal(tree.root)
print("\nPostorder traversal:")
tree.postorder_traversal(tree.root)

# 输出叶子节点及个数
leaves_num = tree.count_leaves(tree.root)
print(f"\nLeaves ({leaves_num}):")
tree.inorder_traversal(tree.root)
print()

# 输出树高
tree_height = tree.height(tree.root)
print(f"Tree height: {tree_height}")

运行程序，输出如下：

Preorder traversal:
50 30 20 40 70 60 80 
Inorder traversal:
20 30 40 50 60 70 80 
Postorder traversal:
20 40 30 60 80 70 50 
Leaves (4):
20 40 60 80 
Tree height: 3

希望这个例子能帮助你理解二叉树的基本操作。