Top Tree View

import java.util.*;
import java.io.*;

class Node {
    Node left;
    Node right;
    int data;

    Node(int data) {
        this.data = data;
        left = null;
        right = null;
    }
}

class Solution {

    /*

    class Node
        int data;
        Node left;
        Node right;
    */
    public static void topView(Node root) {
      int shift = 0;
      int level = 0;
      LinkedHashMap<Node, Integer> nodeLevel = new LinkedHashMap<>();
      LinkedHashMap<Integer, Node> nodeShift = new LinkedHashMap<>();

      LinkedList<Node> lefts = new LinkedList<>();
      LinkedList<Integer> leftLevel = new LinkedList<>();
      LinkedList<Integer> leftShift = new LinkedList<>();

      Node current = root;
      Node other;

      while (true) {
          //System.out.println(current.data);

          if (current.left != null) {
              lefts.add(current.left);
              leftLevel.addLast(level + 1);
              leftShift.addLast(shift - 1);
          }

          if (!nodeShift.containsKey(shift)) {
              nodeShift.put(shift, current);
              nodeLevel.put(current, level);
          } else {
              other = nodeShift.get(shift);
              if (level < nodeLevel.get(other)) {
                  nodeShift.put(shift, current);
                  nodeLevel.remove(other);
                  nodeLevel.put(current, level);
              }
          }

          if (current.right == null) {
              if (lefts.isEmpty()) {
                  break;
              }
              current = lefts.getLast();
              level = leftLevel.getLast();
              shift = leftShift.getLast();
              lefts.removeLast();
              leftLevel.removeLast();
              leftShift.removeLast();
              continue;
          }

          current = current.right;
          level++;
          shift++;
      }

      List<Map.Entry<Integer, Node>> nodes = new ArrayList<>(nodeShift.entrySet());

      Collections.sort(nodes, new Comparator<Map.Entry<Integer, Node>>() {
          public int compare(Map.Entry<Integer, Node> a, Map.Entry<Integer, Node> b) {
              return a.getKey() - b.getKey();
          }
      });

      nodes.forEach(i -> System.out.print(i.getValue().data + " "));

    }


    public static Node insert(Node root, int data) {
        if(root == null) {
            return new Node(data);
        } else {
            Node cur;
            if(data <= root.data) {
                cur = insert(root.left, data);
                root.left = cur;
            } else {
                cur = insert(root.right, data);
                root.right = cur;
            }
            return root;
        }
    }

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int t = scan.nextInt();
        Node root = null;
        while(t-- > 0) {
            int data = scan.nextInt();
            root = insert(root, data);
        }
        scan.close();
        topView(root);
    }
}