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maximum-depth-of-binary-tree_104.py
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maximum-depth-of-binary-tree_104.py
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# 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
# ---------------------------------------Runtime 52 ms Beats 83.74% Memory 19 MB Beats 12.97%---------------------------------------
from typing import Optional
class TreeNode:
def __init__(self, val=0, left=None, right=None):
self.val = val
self.left = left
self.right = right
# Time complexity O(n)
class Solution:
def maxDepth(self, root: Optional[TreeNode]) -> int:
def inner(node, depth=0):
if not node:
return depth
return max(
inner(node.left, depth=depth + 1),
inner(node.right, depth=depth + 1),
)
return inner(root)
# Solution neetcode
# Type Stack
class Solution:
def maxDepth(self, root: Optional[TreeNode]) -> int:
res = 0
stack = [[root, res]]
while stack:
node, depth = stack.pop()
if node:
res = max(res, depth)
stack.append([node.left, depth + 1])
stack.append([node.right, depth + 1])
return res