Build a Binary Tree from Descriptions

Problem Statement

You are given a 2D array descriptions where each descriptions[i] = [parent, child, isLeft] indicates that parent is the parent of child. If isLeft == 1, then child is the left child of parent; otherwise, child is the right child.

Construct the binary tree and return the root node of the resulting tree.

It is guaranteed that the tree is valid, has no cycles, and the root node is unique.

Function Signature

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

def createBinaryTree(descriptions: list[list[int]]) -> TreeNode:

Examples

Example 1: Input: descriptions = [[20,15,1],[20,17,0],[50,20,1],[50,80,0]] Output: A tree with root 50, where 50 has children 20 (left) and 80 (right), 20 has children 15 (left) and 17 (right).

Example 2: Input: descriptions = [[1,2,1],[2,3,0],[3,4,1]] Output: A tree structure where 1 -> 2 (left) -> 3 (right) -> 4 (left).

Constraints

• 1 <= descriptions.length <= 10^4
• 1 <= parent, child <= 10^5
• isLeft is either 0 or 1.

Edge Cases

• A single-node tree or a skewed tree (all nodes only have one child).
• Ensuring the root is the node that never appears as a child in the input array.