binary tree

import java.util.HashMap;
import java.util.LinkedList;
import java.util.Queue;

public class Main {


        static class Node{
            int data;
            top_view_binary_tree.Node left;
            top_view_binary_tree.Node right;
            public Node(int data){
                this.data=data;
                this.left=null;
                this.right=null;
            }

        }
        static class info{
            top_view_binary_tree.Node node;
            int hzd;
            public info(top_view_binary_tree.Node node, int hzd){
                this.node=node;
                this.hzd=hzd;
            }
        }

        // public static Node root=new Node();
        public static void top_view(top_view_binary_tree.Node root) {




            Queue<top_view_binary_tree.info> q=new LinkedList<>();
            HashMap<Integer, top_view_binary_tree.Node> map=new HashMap<>();
            int min=0,max=0;
            q.add(new top_view_binary_tree.info(root,0));
            q.add(null );
            while(!q.isEmpty()){
                top_view_binary_tree.info curr=q.remove();
                if(curr==null){
                    if(q.isEmpty()){
                        break;
                    }
                    else{
                        q.add(null);
                    }
                }
                else{
                    if(!map.containsKey(curr.hzd)){
                        map.put(curr.hzd,curr.node);
                    }
                    if(curr.node.left != null){
                        q.add(new top_view_binary_tree.info(curr.node.left,curr.hzd-1));
                        min=Math.min(min, curr.hzd-1);
                    }
                    if(curr.node.right!=null){
                        q.add(new top_view_binary_tree.info(curr.node.right,curr.hzd+1));
                        max=Math.max(max,curr.hzd+1);
                    }
                }

            }
            for(int i=min;i<=max;i++){
                System.out.print(map.get(i).data+" ");

            }


        }




        public static void main(String args[]){

            top_view_binary_tree.Node root=new top_view_binary_tree.Node(1);
            root.left=new top_view_binary_tree.Node(2);
            root.right=new top_view_binary_tree.Node(3);
            root.left.left=new top_view_binary_tree.Node(4);
            root.right.left=new top_view_binary_tree.Node(6);
            root.left.right=new top_view_binary_tree.Node(5);
            root.right.right=new top_view_binary_tree.Node(7);
            top_view(root);

        }



}