Binary Search Tree

// ConsoleApplication4.cpp : 定義主控台應用程式的進入點。
//

#include "stdafx.h"
#include <iostream>
using namespace std;

class treenode
{
public:
    int value=NULL;
    treenode *l=NULL, *r=NULL;
};

class tree
{
public:
    void append(int);
    void InOrder(treenode*);
    void PreOrder(treenode*);
    void PostOrder(treenode*);
    treenode *root = new(treenode);
private:
};

void tree::append(int in)
{
    treenode* pos = root;
    if (root->value == NULL)
    {
        root->value = in;
        cout << "append " << in << " to root" << endl;
        goto end;
    }
    while (true)
    {
        if (pos->value < in)
        {
            if (pos->l != NULL)
            {
                pos = pos->l;
            }
            else
            {
                pos->l = new(treenode);
                pos->l->value = in;
                cout << "append " << in << endl;
                goto end;
            }
        }
        else if (pos->value > in)
        {
            if (pos->r != NULL)
            {
                pos = pos->r;
            }
            else
            {
                pos->r = new(treenode);
                pos->r->value = in;
                cout << "append " << in << endl;
                goto end;
            }
        }
        else
        {
            cout << pos->value << ' ' << in;
            cout << "append same value\n";
            goto end;
        }
    }
    end:
        return;
}

void tree::InOrder(treenode *pos)
{
    if (pos != NULL)
    {
        InOrder(pos->l);
        cout << '[' << pos->value << ']';
        InOrder(pos->r);
    }
}

void tree::PreOrder(treenode *pos)
{
    if (pos != NULL)
    {
        cout << '[' << pos->value << ']';
        PreOrder(pos->l);
        PreOrder(pos->r);
    }
}
void tree::PostOrder(treenode *pos)
{
    if (pos != NULL)
    {
        PostOrder(pos->l);
        PostOrder(pos->r);
        cout << '[' << pos->value << ']';
    }
}

int main()
{
    tree ta;
    ta.append(50);
    ta.append(40);
    ta.append(30);
    ta.append(45);
    ta.append(48);
    ta.append(65);
    ta.append(70);
    ta.InOrder(ta.root);
    cout << endl;
    ta.PreOrder(ta.root);
    cout << endl;
    ta.PostOrder(ta.root);
    cout << endl;
    return 0;
}