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g2101_2200.s2196_create_binary_tree_from_descriptions.readme.md Maven / Gradle / Ivy

2196\. Create Binary Tree From Descriptions

Medium

You are given a 2D integer array `descriptions` where descriptions[i] = [parenti, childi, isLefti] indicates that parenti is the **parent** of childi in a **binary** tree of **unique** values. Furthermore,

*   If isLefti == 1, then childi is the left child of parenti.
*   If isLefti == 0, then childi is the right child of parenti.

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:**

![](https://assets.leetcode.com/uploads/2022/02/09/example1drawio.png)

**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:**

![](https://assets.leetcode.com/uploads/2022/02/09/example2drawio.png)

**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 <= 104
*   `descriptions[i].length == 3`
*   1 <= parenti, childi <= 105
*   0 <= isLefti <= 1
*   The binary tree described by `descriptions` is valid.