bst_from_preorder.py

from bst_node import BstNode
from test_framework import generic_test


def rebuild_bst_from_preorder(preorder_sequence):

    if not preorder_sequence:
        return None

    transition_point = next((i for i, a in enumerate(preorder_sequence)
                             if a > preorder_sequence[0]),
                            len(preorder_sequence))
    return BstNode(
        preorder_sequence[0],
        rebuild_bst_from_preorder(preorder_sequence[1:transition_point]),
        rebuild_bst_from_preorder(preorder_sequence[transition_point:]))


if __name__ == '__main__':
    exit(
        generic_test.generic_test_main("bst_from_preorder.py",
                                       'bst_from_preorder.tsv',
                                       rebuild_bst_from_preorder))