Leetcode problem: Create Binary Tree From Descriptions

Problem statement:

You are given a 2D integer array descriptions where descriptions[i] = [parent_i, child_i, isLeft_i] indicates that parent_i is the parent of child_i in a binary tree of unique values. Furthermore,

• If isLeft_i == 1, then child_i is the left child of parent_i.
• If isLeft_i == 0, then child_i is the right child of parent_i.

Construct the binary tree described by descriptions and return its root.

The test cases will be generated such that the binary tree is valid.

Example 1:

Input: descriptions = [[20,15,1],[20,17,0],[50,20,1],[50,80,0],[80,19,1]]
Output: [50,20,80,15,17,19]
Explanation: The root node is the node with value 50 since it has no parent.
The resulting binary tree is shown in the diagram.

Example 2:

Input: descriptions = [[1,2,1],[2,3,0],[3,4,1]]
Output: [1,2,null,null,3,4]
Explanation: The root node is the node with value 1 since it has no parent.
The resulting binary tree is shown in the diagram.

Constraints:

• 1 <= descriptions.length <= 10^4
• descriptions[i].length == 3
• 1 <= parent_i, child_i <= 10^5