Solution Files

You can find the solutions in hw06.py.

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 s0 = [1, 2, 3] and s1 = [4, 5, 6], then 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'
    half = len(s) // 2
    shuffled = []
    for i in range(half):
        shuffled.append(s[i])
        shuffled.append(s[half + i])
    return shuffled

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 applying f to each number within s and replacing the number with the result of calling f on that number.

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
    """
    for i in range(len(s)):
        if type(s[i]) == list:
            deep_map(f, s[i])
        else:
            s[i] = f(s[i])

Use Ok to test your code:

python3 ok -q deep_map
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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.

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