104. Maximum Depth of Binary Tree

문제

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, 104].
• -100 <= Node.val <= 100

풀이

재귀함수를 사용하여 트리를 순회하면서 깊이를 측정한다.

class Solution:
    def maxDepth(self, root: TreeNode) -> int:
        if root == None :
            return 0
        else :
            left = 0
            right = 0
            if root.left != None :
                left = self.maxDepth(root.left)

            if root.right != None :
                right = self.maxDepth(root.right)
            return 1 + max(left, right)