2025-07-30 17:35:12 +0000 UTC

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def mergeTrees(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> Optional[TreeNode]:
        if root1 is None:
            return root2
        if root2 is None:
            return root1
        queue = [(root1, root2)]
        while queue:
            node1, node2 = queue.pop()
            if node1 is None or node2 is None:
                continue
            node1.val += node2.val
            if node1.left is None:
                node1.left = node2.left
            else:
                queue.append((node1.left, node2.left))
            if node1.right is None:
                node1.right = node2.right
            else:
                queue.append((node1.right, node2.right))
        return root1