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Returning a pointer to an object

Rishav Paul (24)
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#include<iostream>
using namespace std;

class btree
{
      struct node
      {
             node *left;
             int data;
             node *right;
      };
      
      public:
             node *root;
             btree();
             void insert(node*,int);
             void inorder(node*);
             /*void postorder(node*);
             void preorder(node*);
             void del(node*);*/
             node* find(node*,int);
};

btree::btree()
{
             root=NULL;
}

node* btree::find (node *temp, int item)
{
      if(temp==NULL)
      return temp;
      else if(temp->data==item)
      return temp;
      else if(temp->data<item)
      {
           if(temp->right==NULL)
           return temp;
           else return find(temp->right,item);
      }
      else 
      {
           if(temp->left==NULL)
           return temp
           else return find(temp->left,item);
      }
}
      
void btree:: insert(node *temp, int item)
{
     node *place=find(temp,item);
     
     if(place==NULL)
     {
                   temp=new node;
                   temp->data=item;
                   temp->right=NULL;
                   temp->left=NULL;
                   root=temp;
     }
     
     if(item<place->data)
     {
                     place->left=new node;
                     place->left->data=item;
                     place->left->left=NULL;
                     place->left->right=NULL;
     }   
     
     if(item>place->data)
     {
                     place->right=new node;
                     place->right->data=item;
                     place->right->left=NULL;
                     place->right->right=NULL;
     }
}                               

void btree::inorder(node *temp)
{
     if(temp==NULL)
     return;
     else
     {
         inorder(temp->left);
         cout<<temp->data<<" ";
         inorder(temp->right);
     }
}                   
     
int main()
{
    btree a;
    for(int i=1;i<100;i++)
    a.insert(a.root,i);
    
    a.inorder(a.root);
    system("pause");
    return 0;
}
                   


29 C:\Dev-Cpp\BST.cpp expected constructor, destructor, or type conversion before "btree" 
29 C:\Dev-Cpp\BST.cpp expected `,' or `;' before "btree"


// Why am I getting this error? Where am I going wrong?
Last edited on
Rishav Paul (24)
My question is not showing up on the forum. :( Someone help please..
Peter87 (11234)
The return type on line 29 should be btree::node. You are missing a semicolon on line 44.
Rishav Paul (24)
Returning a pointer to an object
Remove #include<iostream> using namespace std; class btree { struct node { ...
Sep 9, 2012 at 4:34pm [2 replies] Last: The return type on line 29 should be btree::node . You are missing a ... (by Peter87)

Hey Peter,
In the My Topics page, all I can see is that^, but when I open this page, I can see only my comment and question. What is the problem? Please PM me. I'm new on this site.
Thanks
Rishav Paul (24)
oops! now found it.. had to refresh the page after opening it once.. weird!
Rishav Paul (24)
nope.. it is still not working.. if I do modify line 29 to be btree::node, that would mean that the function would return an integer, whereas I am returning a pointer to a node.
Peter87 (11234)
Sorry, I mean btree::node*.
Rishav Paul (24)
That is not working as well .. Too many errors.. Can you please compile the program once and check?
Last edited on
Peter87 (11234)
When I do the two changes the program compiles for me. It crash if I try to run it though.
Last edited on
Rishav Paul (24)
node* find(node*,int); btree::node* find (node *temp, int item)

Is this the final thing? I have made the other ";" entry. Program still does not compile.
Peter87 (11234)
What error message do you get?
Rishav Paul (24)
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#include<iostream>
using namespace std;

class btree
{
      
      struct node
      {
             node *left;
             int data;
             node *right;
      };
      
      public:
             node *root;
             btree();
             void insert(node*,int);
             void inorder(node*);
             /*void postorder(node*);
             void preorder(node*);
             void del(node*);*/
             node* find(node*,int);
};

btree::btree()
{
             root=NULL;
}

btree::node* find (node *temp, int item)
{
      if(temp==NULL)
      return temp;
      else if(temp->data==item)
      return temp;
      else if(temp->data<item)
      {
           if(temp->right==NULL)
           return temp;
           else return find(temp->right,item);
      }
      else 
      {
           if(temp->left==NULL)
           return temp;
           else return find(temp->left,item);
      }
}
      
void btree:: insert(node *temp, int item)
{
     node *place=find(temp,item);
     
     if(place==NULL)
     {
                   temp=new node;
                   temp->data=item;
                   temp->right=NULL;
                   temp->left=NULL;
                   root=temp;
     }
     
     if(item<place->data)
     {
                     place->left=new node;
                     place->left->data=item;
                     place->left->left=NULL;
                     place->left->right=NULL;
     }   
     
     if(item>place->data)
     {
                     place->right=new node;
                     place->right->data=item;
                     place->right->left=NULL;
                     place->right->right=NULL;
     }
}                               

void btree::inorder(node *temp)
{
     if(temp==NULL)
     return;
     else
     {
         inorder(temp->left);
         cout<<temp->data<<" ";
         inorder(temp->right);
     }
}                   
     
int main()
{
    btree a;
    for(int i=1;i<100;i++)
    a.insert(a.root,i);
    
    a.inorder(a.root);
    system("pause");
    return 0;
}
                   


30 C:\Dev-Cpp\BST.cpp `node' was not declared in this scope 
30 C:\Dev-Cpp\BST.cpp `temp' was not declared in this scope 
30 C:\Dev-Cpp\BST.cpp expected primary-expression before "int" 
31 C:\Dev-Cpp\BST.cpp initializer expression list treated as compound expression 
31 C:\Dev-Cpp\BST.cpp expected `,' or `;' before '{' token
Peter87 (11234)
You should not remove btree:: in front of find.
btree::node* btree::find(node *temp, int item)
Last edited on
Rishav Paul (24)
Hey.. Why do we do that? I do not get the reason behind it.. The program does compile now but there is no output..
Peter87 (11234)
Rishav Paul wrote:
Why do we do that? I do not get the reason behind it..

The first btree:: is needed because node is defined inside btree. Without btree:: it thinks we mean node in the global namespace, which is not defined so you get an error message.

The second btree:: is needed because we want to define a member function of btree, not a non-member function in the global namespace.

Rishav Paul wrote:
The program does compile now but there is no output..

The program crashes because you try to use a null pointer on line 63.
Last edited on
Rishav Paul (24)
wow! I did get the reason why we use the scope operator twice. Thank you so much.

On line 63, I have if(item<place->data).. I should use else if I suppose..
Rishav Paul (24)
I got the output! :) "Happiest man on Earth " now. Thank you so much. Lot of concepts got cleared today. But I will be needing more help I'm sure
Rishav Paul (24)
Sir, how is the logic behind my program? Is it too basic? Can it be done in a more elegant and short manner using lesser memory/time?
Peter87 (11234)
I guess this is a school assignment so don't worry too much about memory/time efficiency. Elegant and easy to read code is much more important. It's probably possible write the find function a bit shorter but it's no big deal in my opinion.

The indentation doesn't look perfect (maybe it's just an issue when copying it to this site?).
Rishav Paul (24)
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#include<iostream>
using namespace std;

class btree
{
      public:
      struct node
      {
             node *left;
             int data;
             node *right;
      };
            
             node *root;
             btree();
             void insert(node*,int);
             void inorder(node*);
             void postorder(node*);
             void preorder(node*);
             void del(node*);
             node* find(node*,int);
};

btree::btree()
{
             root=NULL;
}

btree::node* btree::find(node *temp, int item)
{
      if(temp==NULL)
             return temp;
             
      else if(temp->data<item)
      {
             if(temp->right!=NULL)
             return find(temp->right,item);
      }
      else 
      {
             if(temp->left!=NULL)
             return find(temp->left,item);
      }
      return temp;
}
      
void btree:: insert(node *temp, int item)
{
     node *place=find(temp,item);
     
     if(place==NULL)
     {
             temp=new node;
             temp->data=item;
             temp->right=NULL;
             temp->left=NULL;
             root=temp;
     }
     
     else if(item<place->data)
     {
             place->left=new node;
             place->left->data=item;
             place->left->left=NULL;
             place->left->right=NULL;
     }   
     
     else if(item>place->data)
     {
             place->right=new node;
             place->right->data=item;
             place->right->left=NULL;
             place->right->right=NULL;
     }
}                               

void btree::inorder(node *temp)
{
     if(temp==NULL)
            return;
     else
     {
            inorder(temp->left);
            cout<<temp->data<<" ";
            inorder(temp->right);
     }
}

void btree::preorder(node *temp)
{
     if(temp==NULL)
            return;
     else
     {
            cout<<temp->data<<" ";
            preorder(temp->left);
            preorder(temp->right);
     }
}

void btree::postorder(node *temp)
{
     if(temp==NULL)
            return;
     else
     {
            postorder(temp->left);
            postorder(temp->right);
            cout<<temp->data<<" ";
     }
}                         
     
int main()
{
    btree a;
    
    a.insert(a.root,9);
    a.insert(a.root,3);
    a.insert(a.root,6);
    a.insert(a.root,1);
    a.insert(a.root,8);
    a.insert(a.root,2);
    a.insert(a.root,5);
    a.insert(a.root,7);
    a.insert(a.root,4);
    a.insert(a.root,10);
    
    a.inorder(a.root);
    cout<<endl;
    a.preorder(a.root);
    cout<<endl;
    a.postorder(a.root);
    cout<<endl;
    system("pause");
    return 0;
}


Is the indentation proper now? I never really learnt this thing.
I have modified the find() function. Is that what you were talking about?
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