C# 先序Create二叉树问题（抢分贴）

Question

下面的函数都跑过没问题，传值有问题，最终主函数的node孩子为空...(红色语句出问题，呵呵)，达人帮忙看下，不自己想啦~
using System;
using System.Collections.Generic;
using System.Text;namespace Tree
{
    class BinaryTreeNode
    {
        public int value;
        public BinaryTreeNode leftchild;
        public BinaryTreeNode rightchild;        public BinaryTreeNode()
        {
            this.value = 0;
            this.leftchild = null;
            this.rightchild = null;
        }
    }    class Program
    {
        static int[] arr = { 1, 2, 0, 0, 3};        static int i = -1;        static void Main(string[] args)
        {
            BinaryTreeNode node = new BinaryTreeNode();
            CreateBinaryTree(node);
            Console.WriteLine(node.leftchild.value);
        }        public static void CreateBinaryTree(BinaryTreeNode p)
        {
            i = i + 1;            if (i < arr.Length)
            {
                if (arr[i] == 0)
                {
                    p = null;
                }
                else
                {
                    if (i != 0)
                        p = new BinaryTreeNode();
                    p.value = arr[i];
                    CreateBinaryTree(p.leftchild);
                    CreateBinaryTree(p.rightchild);
                }
            }
        }
    }
}

Answer 1

沙发，代码里不出色，汗~就这： Console.WriteLine(node.leftchild.value);函数很顺~

Answer 2

using System;
using System.Collections.Generic;
using System.Text;namespace Tree
{
    class BinaryTreeNode
    {
        public int value;        public BinaryTreeNode leftchild;
        public BinaryTreeNode rightchild;        public BinaryTreeNode()
        {
            this.value = 0;        }
    }    class Program
    {
        static int[] arr = { 1, 2, 0, 0, 3};        static int i = -1;        static void Main(string[] args)
        {
            BinaryTreeNode node = new BinaryTreeNode();            CreateBinaryTree(ref node);            Console.WriteLine(node.leftchild.value);
        }        public static void CreateBinaryTree(ref BinaryTreeNode p)
        {
            i = i + 1;            if (i < arr.Length)
            {
                if (arr[i] == 0)
                {
                    p = null;
                }
                else
                {
                    if (i != 0)
                        p = new BinaryTreeNode();
                    p.value = arr[i];
                    CreateBinaryTree(ref p.leftchild);
                    CreateBinaryTree(ref p.rightchild);
                }
            }
        }
    }
}

Answer 3

类似当年C语言著名的问题.参数是传char**还是传char*