0104 - Maximum Depth of Binary Tree.py

# 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 maxDepth(self, root: Optional[TreeNode]) -> int:
        if not root:
            return 0
        else:
            leftDepth = self.maxDepth(root.left)
            rightDepth = self.maxDepth(root.right)

        return max(leftDepth, rightDepth) + 1

class Solution2:
    def maxDepth(self, root: Optional[TreeNode]) -> int:
        def dfs(node):
            if not node:
                return 0
            if not node.left and not node.right:
                return 1
            return 1 + max(dfs(node.left), dfs(node.right))

        return dfs(root)