def test_bst(self):
bst = BST()
bst.insert(5, 6)
bst.insert(3, 7)
bst.insert(2, 8)
bst.insert(4, 9)
bst.insert(8, 10)
bst.insert(6, 11)
bst.insert(9, 12)
self.assertTrue(bst.get(6) == 11)
self.assertTrue(bst.get(15) == None)
self.assertTrue(bst.height() == 3)
self.assertTrue(bst.preorder() == [5, 3, 2, 4, 8, 6, 9])
def minimum_cost_tree(keys, frequencies):
A = minimum_cost_matrix(keys, frequencies)
bst = BST()
create_optimal_tree(A, bst, keys, 0, len(keys) - 1)
return bst.preorder()