Deserialize Binary Tree

Problem

Rebuild a binary tree from its preorder serialization and return it in level-order form.

data is a preorder list produced with explicit None markers for missing children. Reconstruct the tree recursively, then emit a LeetCode-style level-order list with None gaps and trailing Nones trimmed. An empty or [None] input returns [].

Return the level-order representation.

Hint

A position pointer that advances on every value or None makes the recursive rebuild simple.

Test cases

case 1

in: [[1,2,null,null,3,null,null]]

expected: [1,2,3]

case 2

in: [[1,null,null]]

expected: [1]

case 3

in: [[]]

expected: []

case 4

in: [[1,null,2,null,null]]

expected: [1,null,2]

Starter codePython

def deserialize_tree(data):
    # Your code here
    pass

4 test cases · run your code against them in the editor