104 Maximum Depth of Binary Tree

# 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
from collections import deque
# time O(O) space O(N)
class Solution:
    def maxDepth(self, root: TreeNode) -> int:
        if not root:
            return 0
        q = deque()
        q.append(root)
        h = 0
        while q:
            h+= 1
            size = len(q)
            for i in range(size):
                node = q.popleft()
                if node.left:
                    q.append(node.left)
                if node.right:
                    q.append(node.right)
        return h

# 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:
# time O(lgN) space O(1) 
    def maxDepth(self, root: TreeNode) -> int:
        if not root:
            return 0
        return  1 + max(self.maxDepth(root.left),self.maxDepth(root.right))