How to make a function that returns all marks on a certain depth of a binary tree in Python

Question

I'm trying to retake my Python exams and i've never really gotten the hang of binary trees.For one exercise i have to make a function that takes an int and a tree as args and returns a list of each node mark on the specified depth.

i have the basic

@dataclass
class Node:
    mark: Any
    left: Optional['Node']
    right: Optional['Node']

to work with. I know how to determine max depth of a binary tree

def maxDepth(node:Node):
    if node is None:
        return -1
    else :
        lDepth = maxDepth(node.left)
        rDepth = maxDepth(node.right)
 
        if (lDepth > rDepth):
            return lDepth+1
        else:
            return rDepth+1

and tried using that with a while loop to stop at a certain depth.

def layer(n:int,node:Node):
    result=[]
    depth=maxDepth(node)
    while depth != n:
        new_depth=maxDepth(node)
    result.append(node)
    return result

but my code makes no sense. I've also thought if i could make a recursive depth-finding function that also counts each time it's called, but have no idea how to implement that. Any help is welcome, i don't want the direct solution, but if you could point me in the right direction that would be great :)

Answer 1

I think that something like this might help:

from typing import Any, Optional

class Node:
    mark: Any
    left: Optional['Node']
    right: Optional['Node']

def traverse_tree(node:Node,currentDepth:int,desiredDepth:int):
    if node != None:
        traverse_tree(node.left,currentDepth+1,desiredDepth)
        traverse_tree(node.right,currentDepth+1,desiredDepth)
        if currentDepth==desiredDepth:
            print(node)

You just have to start off with currentDepth as 0 and this code will traverse the tree, printing those elements with the desired depth.