LeetCode 104 Maximum Depth of Binary Tree

LeetCode 104 Maximum Depth of Binary Tree

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

Example 3:

**Input:** root = []
**Output:** 0

Example 4:

**Input:** root = [0]
**Output:** 1

Constraints:

• The number of nodes in the tree is in the range [0, 10<sup>4</sup>].
• -100 <= Node.val <= 100

题目大意：

求二叉树高度。

解题思路：

公式dfs(root)=1+max(dfs(root.left),dfs(root.right))

Python代码：

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

算法分析：

时间复杂度为O(n)，空间复杂度O(1)。