Print Nodes in Top view of Binary tree.cpp

#include <bits/stdc++.h> 
using namespace std; 
struct Node 
{ 
    Node * left; 
    Node* right; 
    int hd; 
    int data; 
}; 
Node* newNode(int key) 
{ 
    Node* node=new Node(); 
    node->left = node->right = NULL; 
    node->data=key; 
    return node; 
} 
void topview(Node* root) 
{ 
    if(root==NULL) 
       return; 
     queue<Node*>q; 
     map<int,int> m;  
     int hd=0; 
     root->hd=hd;
     q.push(root); 

    cout<< "The top view of the tree is : \n"; 

    while(q.size()) 
    { 
        hd=root->hd; 
        if(m.count(hd)==0)   
        m[hd]=root->data; 
        if(root->left) 
        { 
            root->left->hd=hd-1; 
            q.push(root->left); 
        } 
        if(root->right) 
        { 
            root->right->hd=hd+1; 
            q.push(root->right); 
        } 
        q.pop(); 
        root=q.front(); 

    } 
    for(auto i=m.begin();i!=m.end();i++) 
    { 
        cout<<i->second<<" "; 
    } 

} 
int main() 
{ 
    Node* root = newNode(1); 
    root->left = newNode(2); 
    root->right = newNode(3); 
    root->left->right = newNode(4); 
    root->left->right->right = newNode(5); 
    root->left->right->right->right = newNode(6); 
    cout<<"Following are nodes in top view of Binary Tree\n";  
    topview(root); 
    return 0; 
} 

//Input Format:
//Enter the value of the nodes of the binary tree.

//Output Format:
//Top view of Binary tree.

//Sample Input Format:
//        1
//      /   \
//    2       3
//      \   
//        4  
//          \
//            5
//             \
//               6

//Sample Output Format:
//Top view of the above binary tree is
//2 1 3 6