Binary tree — இரண்டு குழந்தைகள் வரை

ஒவ்வொரு node-க்கும் left/right (None இருக்கலாம்).

Try this in Python

from __future__ import annotations
from dataclasses import dataclass


@dataclass
class TreeNode:
    val: int
    left: TreeNode | None = None
    right: TreeNode | None = None


def preorder_vals(root: TreeNode | None) -> list[int]:
    if not root:
        return []
    return [root.val] + preorder_vals(root.left) + preorder_vals(root.right)

r = TreeNode(1, TreeNode(2), TreeNode(3, TreeNode(4)))
print(preorder_vals(r))

Key takeaways

• Skewed tree — recursion depth.
• Iterative — stack/queue.
• Empty tree semantics.