Day28_Maximum Depth of Binary Tree.py

# Maximum Depth of Binary Tree                          Difficulty = Easy






# Given the root of a binary tree, return its maximum depth.

# A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

 

# Example 1:


# Input: root = [3,9,20,null,null,15,7]
# Output: 3
# Example 2:

# Input: root = [1,null,2]
# Output: 2


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