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# Class representing a single node of the binary tree
class Node:
    # Constructor to initialize node with value
    def __init__(self, val):
        self.data = val
        self.left = None
        self.right = None

# Class containing the logic for top view
class Solution:
    # Function to return the top view of the binary tree
    def topView(self, root):
        # Create a list to store final answer
        ans = []

        # If tree is empty, return empty list
        if root is None:
            return ans

        # Dictionary to store vertical_level -> node value
        mpp = {}

        # Queue for BFS storing (node, vertical_level)
        from collections import deque
        q = deque()

        # Push the root with vertical level 0
        q.append((root, 0))

        # Start BFS traversal
        while q:
            # Pop the front element from queue
            node, line = q.popleft()

            # If vertical level is first time visited, store value
            if line not in mpp:
                mpp[line] = node.data

            # If left child exists, push with vertical level - 1
            if node.left:
                q.append((node.left, line - 1))

            # If right child exists, push with vertical level + 1
            if node.right:
                q.append((node.right, line + 1))

        # Extract values from dictionary in sorted order of vertical levels
        for key in sorted(mpp.keys()):
            ans.append(mpp[key])

        # Return the result
        return ans

# Driver code
if __name__ == "__main__":
    # Create the sample binary tree
    root = Node(1)
    root.left = Node(2)
    root.left.left = Node(4)
    root.left.right = Node(10)
    root.left.left.right = Node(5)
    root.left.left.right.right = Node(6)
    root.right = Node(3)
    root.right.right = Node(10)
    root.right.left = Node(9)

    # Create Solution object
    solution = Solution()

    # Get the top view
    result = solution.topView(root)

    # Print the result
    print("Top View Traversal:", *result)
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