MaximumDepthOfBinaryTree

Problem

https://leetcode.com/problems/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

Constraints:

• The number of nodes in the tree is in the range [0, 10:sup:`4`].

• -100 <= Node.val <= 100

Solution

If root is None, the height of a tree is 0. Otherwise, the height of a tree is the 1 plus the maximum of the heights of the left and right subtrees.

Pattern

Tree, Depth-First Search, Breadth-First Search, Binary Tree

Code

class TreeNode:
    """Node in a binary tree.
    """

    def __init__(self, val, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right


def maxDepth(root: TreeNode | None) -> int:
    """Find the maximum depth or total height of a binary tree.
    """
    if root is None:
        return 0
    return 1 + max(maxDepth(root.left), maxDepth(root.right))

Test

>>> from MaximumDepthOfBinaryTree import TreeNode, maxDepth
>>> root = TreeNode(3, TreeNode(9), TreeNode(20, TreeNode(15), TreeNode(7)))
>>> maxDepth(root)
3
>>> root = TreeNode(1, None, TreeNode(2))
>>> maxDepth(root)
2

class MaximumDepthOfBinaryTree.TreeNode(val, left=None, right=None)

Bases: object

Node in a binary tree.

MaximumDepthOfBinaryTree.maxDepth(root: TreeNode | None) → int

Find the maximum depth or total height of a binary tree.