[LeetCode] 617. Merge Two Binary Trees (Python)

• Reference
• return roo1 or root2도 가능

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# Definition for a binary tree node.
from typing import Optional


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 and root2:
            node = TreeNode(root1.val + root2.val)

            node.left = self.mergeTrees(root1.left, root2.left)
            node.right = self.mergeTrees(root1.right, root2.right)

            return node

        if root1:
            return root1

        if root2:
            return root2