104. Maximum Depth of Binary Tree
Đề Bài
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
Constraints:
- The number of nodes in the tree is in the range
[0, 104]. -100 <= Node.val <= 100
Thuật Toán & Kỹ Thuật
⏱️ Thời gian
O(n²)
💾 Không gian
O(1)
Lời Giải
Python
0104-maximum-depth-of-binary-tree.py
# 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:
def maxDepth(self, root: Optional[TreeNode]) -> int:
if not root:
return 0
dq = deque([root])
cnt = 0
while dq:
n = len(dq)
for _ in range(n):
node = dq.popleft()
if node.left:
dq.append(node.left)
if node.right:
dq.append(node.right)
cnt += 1
return cnt