HTMLify

from collections import deque, defaultdict

class Solution:
    def verticalOrder(self, root): 
        if not root:
            return []
            
        hd_map = defaultdict(list)
        
        queue = deque([(root, 0)])
        
        min_hd, max_hd = 0, 0
        
        while queue:
            node, hd = queue.popleft()
            
            hd_map[hd].append(node.data)
            
            min_hd = min(min_hd, hd)
            max_hd = max(max_hd, hd)
            
            if node.left:
                queue.append((node.left, hd - 1))
            if node.right:
                queue.append((node.right, hd + 1))
        
        result = []
        for i in range(min_hd, max_hd + 1):
            if i in hd_map:
                result.append(hd_map[i])
                
        return result