1
class Solution:
2
    def diameterOfBinaryTree(self, root: Optional[TreeNode]) -> int:
3
        ans = 0
4

5
        def dfs(cur) -> int:
6
            nonlocal ans
7
            if cur is None:
8
                return 0
9
            l = dfs(cur.left) + 1
10
            r = dfs(cur.right) + 1
11
            nonlocal ans
12
            ans = max(ans, l + r - 2)
13
            return max(l, r)
14

15
        dfs(root)
16
        return ans

1
class Solution:
2
    def isSame(self, p, q) -> bool:
3
        if p is None or q is None:
4
            return p is q
5
        if p.val != q.val:
6
            return False
7
        return self.isSame(p.left, q.right) and self.isSame(p.right, q.left)
8

9
    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
10
        return self.isSame(root.left, root.right)

1
class Solution:
2
    def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
3
        if root is None:
4
            return None
5
        tmp = deepcopy(root.right)
6
        root.right = self.invertTree(root.left)
7
        root.left = self.invertTree(tmp)
8
        return root

1
class Solution:
2
    def maxDepth(self, root: Optional[TreeNode]) -> int:
3
        if root is None:
4
            return 0
5
        return max(self.maxDepth(root.left) + 1, self.maxDepth(root.right) + 1)

1
class Solution:
2
    def inorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
3
        ans = []
4

5
        def dfs(cur):
6
            if cur is None:
7
                return
8
            dfs(cur.left)
9
            ans.append(cur.val)
10
            dfs(cur.right)
11

12
        dfs(root)
13

14
        return ans