solve

It's still the weekend so taking it easy. Some binary tree questions.

problem

from typing import Optional
# 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 isSymmetric(self, root: Optional[TreeNode]) -> bool:
        return self.is_mirror(root.left, root.right)
    
    def is_mirror(self, p, q):
        if p is None and q is None:
            return True
        elif p is not None and q is None:
            return False
        elif p is None and q is not None:
            return False
        # elif p is not None and q is not None:
        if p.val != q.val:
            return False
        
        return self.is_mirror(p.right, q.left) and self.is_mirror(p.left, q.right)

problem

from typing import Optional
# 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 invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
        if root == None:
            return None
        placeholder = root.left
        root.left = self.invertTree(root.right)
        root.right = self.invertTree(placeholder)
        return root