[Dev-C++] Binary Tree display

[chromatonus 7. <chr...@ho...>]

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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