Due by 11:59pm on Wednesday, March 12

Instructions

Download hw06.zip. Inside the archive, you will find a file called hw06.py, along with a copy of the ok autograder.

Submission: When you are done, submit the assignment by uploading all code files you've edited to Gradescope. You may submit more than once before the deadline; only the final submission will be scored. Check that you have successfully submitted your code on Gradescope. See Lab 0 for more instructions on submitting assignments.

Using Ok: If you have any questions about using Ok, please refer to this guide.

Readings: You might find the following references useful:

• Section 2.4

Grading: Homework is graded based on correctness. Each incorrect problem will decrease the total score by one point. This homework is out of 2 points.

Required Questions

Q1: Shuffle

Implement shuffle, which takes a sequence s (such as a list or range) with an even number of elements. It returns a new list that interleaves the elements of the first half of s with the elements of the second half. It does not modify s.

To interleave two sequences s0 and s1 is to create a new list containing the first element of s0, the first element of s1, the second element of s0, the second element of s1, and so on. For example, if s = [1, 2, 3, 4, 5, 6] then s0 = [1, 2, 3] and s1 = [4, 5, 6], and interleaving s0 and s1 would result in [1, 4, 2, 5, 3, 6].

def shuffle(s):
    """Return a shuffled list that interleaves the two halves of s.

    >>> shuffle(range(6))
    [0, 3, 1, 4, 2, 5]
    >>> letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']
    >>> shuffle(letters)
    ['a', 'e', 'b', 'f', 'c', 'g', 'd', 'h']
    >>> shuffle(shuffle(letters))
    ['a', 'c', 'e', 'g', 'b', 'd', 'f', 'h']
    >>> letters  # Original list should not be modified
    ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']
    """
    assert len(s) % 2 == 0, 'len(seq) must be even'
    "*** YOUR CODE HERE ***"

Use Ok to test your code:

python3 ok -q shuffle
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✂️

Q2: Deep Map

Definition: A nested list of numbers is a list that contains numbers and lists. It may contain only numbers, only lists, or a mixture of both. The lists must also be nested lists of numbers. For example: [1, [2, [3]], 4], [1, 2, 3], and [[1, 2], [3, 4]] are all nested lists of numbers.

Write a function deep_map that takes two arguments: a nested list of numbers s and a one-argument function f. It modifies s in place by replacing each number in s with the result of calling f on that number.

Important:: deep_map returns None and should not create any new lists.

Hint: type(a) == list will evaluate to True if a is a list.

def deep_map(f, s):
    """Replace all non-list elements x with f(x) in the nested list s.

    >>> six = [1, 2, [3, [4], 5], 6]
    >>> deep_map(lambda x: x * x, six)
    >>> six
    [1, 4, [9, [16], 25], 36]
    >>> # Check that you're not making new lists
    >>> s = [3, [1, [4, [1]]]]
    >>> s1 = s[1]
    >>> s2 = s1[1]
    >>> s3 = s2[1]
    >>> deep_map(lambda x: x + 1, s)
    >>> s
    [4, [2, [5, [2]]]]
    >>> s1 is s[1]
    True
    >>> s2 is s1[1]
    True
    >>> s3 is s2[1]
    True
    """
    "*** YOUR CODE HERE ***"

Use Ok to test your code:

python3 ok -q deep_map
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✂️

Q3: Common Players

Implement the function common_players. The common_players function takes in a roster dictionary that maps players to their teams, and returns a new dictionary that maps teams to a list of players on that team. The order of player names in the list does not matter.

def common_players(roster):
    """Returns a dictionary containing values along with a corresponding
    list of keys that had that value from the original dictionary.
    >>> full_roster = {
    ...     "bob": "Team A",
    ...     "barnum": "Team B",
    ...     "beatrice": "Team C",
    ...     "bernice": "Team B",
    ...     "ben": "Team D",
    ...     "belle": "Team A",
    ...     "bill": "Team B",
    ...     "bernie": "Team B",
    ...     "baxter": "Team A"
    ... }
    >>> player_dict = common_players(full_roster)
    >>> type(player_dict) == dict
    True
    >>> for key, val in sorted(player_dict.items()):
    ...     print(key, list(sorted(val)))
    Team A ['baxter', 'belle', 'bob']
    Team B ['barnum', 'bernice', 'bernie', 'bill']
    Team C ['beatrice']
    Team D ['ben']
    """
    "*** YOUR CODE HERE ***"
    

Use Ok to test your code:

python3 ok -q common_players
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✂️

Check Your Score Locally

You can locally check your score on each question of this assignment by running

python3 ok --score

This does NOT submit the assignment! When you are satisfied with your score, submit the assignment to Gradescope to receive credit for it.

Submit Assignment

Submit this assignment by uploading any files you've edited to the appropriate Gradescope assignment. Lab 00 has detailed instructions.