## Problem You are given the preorder and postorder traversals of a binary tree whose node values are distinct. Reconstruct one binary tree consistent with both traversals. Some traversal pairs do not identify a unique tree, so the contract below defines a deterministic choice. ## Function Contract Implement `reconstruct_tree(preorder, postorder)` and return the reconstructed tree as a level-order list. Use `null` for missing children and remove trailing `null` values from the returned list. ## Rules - The inputs describe the same valid binary tree and contain the same distinct values. - For an ambiguous node with exactly one child, attach that child on the left. - For a node with two children, preserve their relative left-to-right order from both traversals. - The returned tree must reproduce the given preorder and postorder traversals exactly. - Do not enumerate all possible trees. ## Constraints - `1 <= len(preorder) == len(postorder) <= 100000`. - All node values are distinct signed 32-bit integers. - Account for linear tree depth rather than assuming a balanced tree. ## Examples ```text preorder = [1, 2, 3] postorder = [3, 2, 1] output = [1, 2, null, 3] ``` The traversals are ambiguous; the deterministic rule places each single child on the left.