Construct Binary Tree from Preorder and Inorder Traversal

Given preorder and inorder traversals of a tree with unique values, construct the tree and return its level-order array.

Examples
Input: [[3,9,20,15,7],[9,3,15,20,7]]
Output: [3,9,20,null,null,15,7]
Hints
Related Problems

Construct Binary Tree from Preorder and Inorder Traversal

Given preorder and inorder traversals of a tree with unique values, construct the tree and return its level-order array.