#2196

Create Binary Tree From Descriptions

pupil · 420 · lc medium +25 · failed · 81.7% accepted · 1,657 likes · top 93%

Description

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

- If isLefti == 1, then childi is the left child of parenti.

- If isLefti == 0, then childi is the right child of parenti.

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

The test cases guarantee 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.

Code

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def createBinaryTree(self, descriptions: List[List[int]]) -> Optional[TreeNode]:

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def createBinaryTree(self, descriptions: List[List[int]]) -> Optional[TreeNode]: