Top View of BST using STL library

topview.cpp

#include<iostream>
#include<cstdlib>
#include<queue>
#include<map>
using namespace std;


struct node{
int data;
struct node *left;
struct node *right;
};

class qitem{
public:
struct node *tnode;
int hd;
qitem(struct node *n,int x)
{

    tnode=n;
    hd=x;
}
};


struct node *newnode(int x)
{
 struct node* ptr=(struct node*)malloc(sizeof(struct node));
    ptr->data=x;
    ptr->left=NULL;
    ptr->right=NULL;
    return ptr;
}

struct node* insert(struct node *root,int x)
{

struct node* par;
    if(root==NULL)
    {
        root=newnode(x);
        return root;
    }
    else
    {
        struct node *proot=root;
        while(proot!=NULL)
        {

            if(x<proot->data)
            {
                par=proot;
                proot=proot->left;

            }
            else
            {
                par=proot;
                proot=proot->right;

            }
        }
         if(x<par->data)
        par->left=newnode(x);
    else
        par->right=newnode(x);

        return root;
    }

}

void display(struct node *root)
{

    if(root==NULL)
        return;
    display(root->left);
    cout<<"\t"<<root->data;
    display(root->right);
}

void topview(struct node *root,map<int,int> &m)
{
    queue<qitem*> q;
    if(root==NULL)
        return;

    q.push(new qitem(root,0));
    while(!q.empty())
    {
        qitem *element=q.front();
        int d=element->hd;
        struct node *n=element->tnode;
        q.pop();
        if(m.count(d)==0)
        m[d]=n->data;
        if(n->left)
        {
            q.push(new qitem(n->left,d-1));
        }
        if(n->right)
        {
            q.push(new qitem(n->right,d+1));
        }

    }

}
int main()
{

    int x;
    map<int,int> mp;
    map<int,int>::iterator it;
     struct node *root=NULL;
        while(1)
        {

           cin>>x;
            if(x==-1)
            break;

            root=insert(root,x);
        }

        display(root);
        cout<<endl;
        topview(root,mp);
        for(it=mp.begin();it!=mp.end();it++)
        {
            cout<<"\t"<<it->second;
        }
}