Merge Two Binary Trees Python Solution

lcpy gen -n 617   # by problem number
lcpy gen -s merge_two_binary_trees   # by problem name

Input: root1 = [1,3,2,5], root2 = [2,1,3,null,4,null,7]
Output: [3,4,5,5,4,null,7]

Input: root1 = [1], root2 = [1,2]
Output: [2,2]

from leetcode_py import TreeNode


class Solution:
    # Time: O(n) where n is the smaller tree's node count
    # Space: O(h)
    def merge_trees(
        self, root1: TreeNode[int] | None, root2: TreeNode[int] | None
    ) -> TreeNode[int] | None:
        if root1 is None:
            return root2
        if root2 is None:
            return root1
        root1.val += root2.val
        root1.left = self.merge_trees(root1.left, root2.left)
        root1.right = self.merge_trees(root1.right, root2.right)
        return root1