Due by 10:00am on Tuesday, 7/12


Download quiz04.zip. Inside the archive, you will find a file called quiz04.py, along with a copy of the OK autograder.

Complete the quiz and submit it before 10:00am on Tuesday, 7/12. You must work alone, but you may talk to the course staff (see Asking Questions below). You may use any course materials, including an interpreter, course videos, slides, and readings. Please do not discuss these specific questions with your classmates, and do not scour the web for answers or post your answers online.

Your submission will be graded automatically for correctness. Your implementations do not need to be efficient, as long as they are correct. We will apply additional correctness tests as well as the ones provided. Though we will not release these hidden tests to you, you will receive autograder feedback specifying whether or not you have passed all tests.

Asking Questions: If you believe you need clarification on a question, make a private post on Piazza. Please do not post publicly about the quiz contents. If the staff discovers a problem with the quiz or needs to clarify a question, we will email the class via Piazza. You can also come to office hours to ask questions about the quiz or any other course material, but no answers or hints will be provided in office hours.

Submission: When you are done, submit with python3 ok --submit. You may submit more than once before the deadline; only the final submission will be scored.

Using OK

The ok program helps you test your code and track your progress. The first time you run the autograder, you will be asked to log in with your @berkeley.edu account using your web browser. Please do so. Each time you run ok, it will back up your work and progress on our servers. You can run all the doctests with the following command:

python3 ok

To test a specific question, use the -q option with the name of the function:

python3 ok -q <function>

By default, only tests that fail will appear. If you want to see how you did on all tests, you can use the -v option:

python3 ok -v

If you do not want to send your progress to our server or you have any problems logging in, add the --local flag to block all communication:

python3 ok --local

When you are ready to submit, run ok with the --submit option:

python3 ok --submit

Readings: You might find the following references useful:

Question 1: Deep Reverse

A linked list that contains one or more linked lists as elements is called a deep linked list. Write a function deep_reverse that takes in a (possibly deep) linked list and returns a new linked list with the elements in reverse order. You may write and use helper functions if you find them useful.

Hint: You may find Lab 5 helpful.

You can check if something is a linked list by using the provided is_link function. For example,

>>> is_link(1)
>>> is_link(empty)
>>> is_link(link(1, link(2, empty)))
def deep_reverse(lnk):
    """Return a reversed version of a possibly deep linked list lnk.

    >>> print_link(deep_reverse(empty))
    >>> print_link(deep_reverse(link(1, link(2, empty))))
    <2 1>

    >>> deep = link(1, link(link(2, link(3, empty)), empty))
    >>> deep_reversed = deep_reverse(deep)
    >>> print_link(first(deep_reversed))
    <3 2>
    >>> first(rest(deep_reversed))
    >>> rest(rest(deep_reversed)) == empty

    "*** YOUR CODE HERE ***"

Use OK to test your code:

python3 ok -q deep_reverse

Question 2: Has Path

Write a function has_path that takes in a tree t and a string word. It returns True if there is a path that starts from the root where the entries along the path spell out the word, and False otherwise.

def has_path(t, word):
    """Return whether there is a path in a tree where the entries along the path
    spell out a particular word.

    >>> greetings = tree('h', [tree('i'),
    ...                        tree('e', [tree('l', [tree('l', [tree('o')])]),
    ...                                   tree('y')])])
    >>> print_tree(greetings)
    >>> has_path(greetings, 'h')
    >>> has_path(greetings, 'i')
    >>> has_path(greetings, 'hi')
    >>> has_path(greetings, 'hello')
    >>> has_path(greetings, 'hey')
    >>> has_path(greetings, 'bye')

    assert len(word) > 0, 'no path for empty words.'
    "*** YOUR CODE HERE ***"

Use OK to test your code:

python3 ok -q has_path