Sum Root to Leaf Numbers Python Solution

lcpy gen -n 129   # by problem number
lcpy gen -s sum_root_to_leaf_numbers   # by problem name

Input: root = [1,2,3]
Output: 25
Explanation:
The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.
Therefore, sum = 12 + 13 = 25.

Input: root = [4,9,0,5,1]
Output: 1026
Explanation:
The root-to-leaf path 4->9->5 represents the number 495.
The root-to-leaf path 4->9->1 represents the number 491.
The root-to-leaf path 4->0 represents the number 40.
Therefore, sum = 495 + 491 + 40 = 1026.

from leetcode_py import TreeNode


class Solution:
    # Time: O(n)
    # Space: O(h)
    def sum_numbers(self, root: TreeNode[int] | None) -> int:
        def dfs(node: TreeNode[int] | None, path_value: int) -> int:
            if node is None:
                return 0
            path_value = path_value * 10 + node.val
            if node.left is None and node.right is None:
                return path_value
            return dfs(node.left, path_value) + dfs(node.right, path_value)

        return dfs(root, 0)