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pass a pointer as call by reference

paulrishav93 (16)
How to pass a pointer as call by reference?

vlad from moscow (6539)
If I have correctly understood what you mean then you can declare a parameter of a function the following way

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void f( int * &x ){}

int i = 10;
int *p = &i;

f( p );
kbw (9488)
EDIT ... vlad from moscow's example is sufficient.
Last edited on
paulrishav93 (16)
This is the problem
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#include<iostream>
using namespace std;

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

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

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

void btree::insert(node *temp,int item)
{
     node* place=find(temp,item);
     
     if(place==NULL)
     {
             temp=new node;
             temp->data=item;
             temp->left=NULL;
             temp->right=NULL;
             root=temp;                
     }
     
     else if(item<place->data)
    // insert(place->left,item);
     {
     place->left=new node;
     place->left->data=item;
     place->left->left=NULL;
     place->left->right=NULL;
     }
     else if(item>place->data)
     //insert(place->right,item);
     {
     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;
    
    a.insert(a.root,5);
    a.insert(a.root,1);
    a.insert(a.root,4);
    a.insert(a.root,2);
    a.insert(a.root,7);
    a.insert(a.root,6);
    a.insert(a.root,3);
    a.inorder(a.root);
    
    system("pause");
    return 0;
}

The above program compiles and runs well

But, the program below does not run. As far as my understanding goes, it is because root is not pointing to the same place as temp

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#include<iostream>
using namespace std;

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

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

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

void btree::insert(node *temp,int item)
{
     node* place=find(temp,item);
     
     if(place==NULL)
     {
             temp=new node;
             temp->data=item;
             temp->left=NULL;
             temp->right=NULL;
             //root=temp;                
     }
     
     else if(item<place->data)
    insert(place->left,item);
     /*{
     place->left=new node;
     place->left->data=item;
     place->left->left=NULL;
     place->left->right=NULL;
     }*/
     else if(item>place->data)
     insert(place->right,item);
    /* {
     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;
    
    a.insert(a.root,5);
    a.insert(a.root,1);
    a.insert(a.root,4);
    a.insert(a.root,2);
    a.insert(a.root,7);
    a.insert(a.root,6);
    a.insert(a.root,3);
    a.inorder(a.root);
    
    system("pause");
    return 0;
}
paulrishav93 (16)
Thanks.. but after applying your suggestions, I have the following program which compiles
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btree::node* btree::find(node *&temp,int item)
{
             if(temp==NULL)
             return temp;
             
             else if(item>temp->data)
            {
                  if (temp->right==NULL)
                 return temp;
                  else return find(temp->right,item);
            }
             
             else if(item<temp->data)
           {
                 if (temp->left==NULL)
                  return temp;
                 else return find(temp->left,item);
            }
             
             else return temp;
}

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


Here root=temp; did not have to be used inside insert function. However, the code below is still non functional
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btree::node* btree::find(node*& temp,int item)
{
             if(temp==NULL)
             return temp;
             
             else if(item>temp->data)
            //{
            //      if (temp->right==NULL)
            //      return temp;
                /*  else*/ return find(temp->right,item);
            // }
             
             else if(item<temp->data)
           // {
           //       if (temp->left==NULL)
           //       return temp;
                  /*  else */return find(temp->left,item);
             //}
             
             else return temp;
}

void btree::insert(node *&temp,int item)
{
     node* place=find(temp,item);
     
     if(place==NULL)
     {
             temp=new node;
             temp->data=item;
             temp->left=NULL;
             temp->right=NULL;
             //root=temp;                
     }
     
     else if(item<place->data)
    insert(place->left,item);
     /*{
     place->left=new node;
     place->left->data=item;
     place->left->left=NULL;
     place->left->right=NULL;
     }*/
     else if(item>place->data)
     insert(place->right,item);
    /* {
     place->right=new node;
     place->right->data=item;
     place->right->left=NULL;
     place->right->right=NULL;
     }*/
}
clanmjc (666)
What exactly is the problem and where is it? What do you mean by non functional?

In your insert, when place == NULL you have found your 'insertion' spot correct? Don't you want place to be the new node and not your temp

Maybe what you need is to have the return type be reference to pointer?

[b]Edit:[/b] Now I see the problem from your other post...
Last edited on
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