using System;

​

public class Node

{

    public int data;

    public Node left;//左子节点指针

    public Node right;//右子节点指针

​

    public Node(int item)

    {

        data = item;

        left = null;

        right = null;

    }

}

​

public class BinaryTree//表示二叉树

{

    public Node root;

​

    public BinaryTree()

    {

        root = null;

    }

​

    public void PreorderTraversal(Node node)//前序遍历（递归）

    {

        if (node == null)

            return;

​

        Console.Write(node.data + " ");

        PreorderTraversal(node.left);

        PreorderTraversal(node.right);

    }

​

    public static void Main()

    {

        BinaryTree tree = new BinaryTree();

​

        // 创建二叉树节点

        tree.root = new Node(1);

        tree.root.left = new Node(2);

        tree.root.right = new Node(3);

        tree.root.left.left = new Node(4);

        tree.root.left.right = new Node(5);

​

        Console.WriteLine("前序遍历结果：");

        tree.PreorderTraversal(tree.root);

    }

}