104MaximumDepthofBinaryTree.py

"""
Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7],

    3
   / \
  9  20
    /  \
   15   7
return its depth = 3.


"""
"""
Comments
"""
"""
My
"""
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None


class Solution:

    def maxDepth(self, root: TreeNode) -> int:
        if root is None:
            return 0
        return 1 + max(self.maxDepth(root.left), self.maxDepth(root.right))
"""
Fast
"""


class Solution:

    def getMax(node, currentDepth) -> 'int':

        # basecase leafnode
        if node.left == None and node.right == None:
            return currentDepth

        else:
            if node.left == None:
                return Solution.getMax(node.right, currentDepth + 1)
            elif node.right == None:
                return Solution.getMax(node.left, currentDepth + 1)
            else:
                return max(Solution.getMax(node.left, currentDepth + 1), Solution.getMax(node.right, currentDepth + 1))

    def maxDepth(self, root: 'TreeNode') -> 'int':
        if root == None:
            return 0
        return Solution.getMax(root, 1)