Re: [Dev-C++] Binary Tree display

[Jason H. <jas...@bt...>]

Hi,

In main you only create one 'new' node for stem, and then you constantly
reuse it, and therefore write over it, every time you insert a node. You
need to create a new node for each new set of data and insert that.

Also in insert_node() you test for root being NULL, which it is to start
with, and then you do:

stem = root;

So the local stem becomes NULL and root doesn't change. I think you meant:

root = stem;

At the moment you aren't actualy inserting anything into the tree, root is
always NULL.

There may be other errors, but are the ones I found after skimming through
it quickly.

Jason.

----- Original Message -----
From: "chromatonus 712" <chr...@ho...>
To: <dev...@li...>
Sent: Wednesday, February 13, 2002 9:28 PM
Subject: [Dev-C++] Binary Tree display


> Hi, I don't know why my screen is not displaying anything after i
supposedly
> input a tree and executed the display commands. Would you please examine
my
> program and see where it's wrong? Thank you!
>
>
> #include <iostream.h>
> #include <stdlib.h>
> #include <conio.h>
>
>
> struct node
> {
>    int data;
>    node *left, *right;
> };
>
>
> //PROTOTYPES
>
> int menu();
>    //postcondition: creates and displays a menu, returning the value of
> choice
>
> void insert_node(node *&, node *);
>
> void pre( node* );
>
> void in( node* );
>
> void post( node* );
>
> int menu()
> {
>    int choice;
>    cout<< "TREE EDITOR MENU OPTIONS" << "\n";
>    cout<< "1.  Insert elements in Tree" << "\n";
>    cout<< "2.  Display Tree in Prefix" << "\n";
>    cout<< "3.  Display Tree in Infix" << "\n";
>    cout<< "4.  Display Tree in Postfix" << "\n";
>    cout<< "5.  Exit";
>    gotoxy(1,8);
>    cout<< "choice? ";
>    cin>> choice;
>    return(choice);
> }
>
> // Main Program
> int main()
> {
>    node *root = NULL;
>    node *stem = new node;
>    int choice, info;
>    choice = menu();
>    while( choice != 5 )
>    {
>       switch( choice )
>       {
>          case 1:  gotoxy(1,10);
>                   cout<< "input?  ";
>                   cin>> info;
>                   stem->data = info;
>                   insert_node(root, stem);
>                   break;
>          case 2:  gotoxy(1,10);
>                   pre( root );
>                   break;
>          case 3:  gotoxy(1,10);
>                   in( root );
>                   break;
>          case 4:  gotoxy(1,10);
>                   post( root );
>                   break;
>       }
>       gotoxy(1,8);
>       cout<< "choice? ";
>       cin>> choice;
>    }
> }
>
> void insert_node(node *&root, node *stem)
> {
>    if(root == NULL)
>    {
>       stem = root;
>    }
>    else
>    {
>       if(stem->data < root->data)
>          insert_node(root->left, stem);
>       else
>          insert_node(root->right, stem);
>    }
> }
>
> void pre(node *root)
> {
>    if( root != NULL )
>    {
>       cout<< root->data <<"  ";
>       pre( root->left );
>       pre( root->right );
>    }
> }
>
> void in(node *root)
> {
>    if( root != NULL )
>    {
>       in(root->left);
>       cout<< root->data <<"  ";
>       in(root->right);
>    }
> }
>
> void post(node *root)
> {
>    if(root != NULL)
>    {
>       post(root->left);
>       post(root->right);
>       cout<< root->data <<"  ";
>    }
> }
>
>
>
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