题解 | 合并二叉树-- leetcode617

# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param t1 TreeNode类 
# @param t2 TreeNode类 
# @return TreeNode类
#
class Solution:
    def mergeTrees(self , t1: TreeNode, t2: TreeNode) -> TreeNode:
        # write code here
        def  dfs(root1,root2):
            # if root1 is None and root2 is None:
            #     return None
            if root1 is None:
                return  root2
            if root2 is None :
                return  root1
            root =TreeNode(root1.val+root2.val)
            root.left=dfs(root1.left,root2.left)
            root.right=dfs(root1.right,root2.right)
            return root 
        # 首先判空处理    
        if not t1:
            return t2 
        if not t2:
            return t1 
        root =dfs(t1,t2) 
        return root