def test_merge():
l = [4, 7, 2, 8, 4, 6, 9, 5, 5, 7, 3, 2, 8]
l_sorted = sorted(l)
l_left = LinkedList.from_list(sorted(l[:5]))
l_right = LinkedList.from_list(sorted(l[5:]))
ll = LinkedList.merge(l_left, l_right)
assert len(ll) == len(l)
for i, j in zip(ll, l_sorted):
assert i == j
def rev_prune_order(self) -> LinkedList["BinaryDecisionTree"]:
"""Iterate over nodes from leaves inwards with each step minimizing
the collapse loss"""
assert not self.terminal, "Can't prune a terminal tree"
if not self.left.terminal:
left_order = self.left.rev_prune_order()
else:
left_order = Nil
if not self.right.terminal:
right_order = self.right.rev_prune_order()
else:
right_order = Nil
return LinkedList(
self,
LinkedList.merge(left_order,
right_order,
key=lambda x: -x.loss_delta_if_collapsed),
)
