Minimum Depth of Binary Tree.py

from typing import Optional


class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right


class Solution:
    """
    Time:   O(n)
    Memory: O(n)
    """

    def minDepth(self, root: Optional[TreeNode]) -> int:
        if root is None:
            return 0

        left_depth = self.minDepth(root.left)
        right_depth = self.minDepth(root.right)

        return 1 + (
            min(left_depth, right_depth) or
            max(left_depth, right_depth)
        )