题目
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.
解题思路
递归：深度为左右子树最大深度+1
非递归：从根开始bfs，每做一层，结果+1
代码
class Solution:
def maxDepth(self, root: TreeNode) -> int:
return max(self.maxDepth(root.left), self.maxDepth(root.right)) + 1 if root else 0
class Solution:
def maxDepth(self, root: TreeNode) -> int:
if not root:
return 0
q = [root]
res = 0
while q:
tq = []
for n in q:
if n.left:
tq.append(n.left)
if n.right:
tq.append(n.right)
q = tq
res += 1
return res
