题解 | #合并二叉树#

# 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
        if not t1 or not t2:
            return t1 or t2
        root = TreeNode(t1.val + t2.val)
        self.dfs(t1.left, t2.left, root, 'left')
        self.dfs(t1.right, t2.right, root, 'right')
        return root

    def dfs(self, t1: TreeNode, t2: TreeNode, root: TreeNode, d: str):
        if d == 'left':
            if not t1 and t2:
                root.left = t2
                return
            elif not t2 and t1:
                root.left = t1
                return
            elif t1 and t2:
                node = TreeNode(t1.val + t2.val)
                root.left = node
                self.dfs(t1.left, t2.left, node, 'left')
                self.dfs(t1.right, t2.right, node, 'right')
            else:
                return
        else:
            if not t1 and t2:
                root.right = t2
                return
            elif not t2 and t1:
                root.right = t1
                return
            elif t1 and t2:
                node = TreeNode(t1.val + t2.val)
                root.right = node
                self.dfs(t1.left, t2.left, node, 'left')
                self.dfs(t1.right, t2.right, node, 'right')
            else:
                return