Hackerrank Collections and Data Structures 3

Question 1

What does `Counter.subtract()` do differently from subtracting two Counters with `-`?

Accepted Answer

subtract() allows negative counts; - removes non-positive counts

Answer

subtract() removes zero/negative counts; - does not

Answer

They are identical in behavior

Answer

subtract() only works with lists, not strings

Question 2

What is the maximum length constraint enforced when creating a `collections.deque` with `maxlen=3` and you append a 4th element?

Accepted Answer

The oldest element on the opposite end is discarded

Answer

Raises IndexError

Answer

The new element is silently ignored

Answer

maxlen doubles automatically

Question 3

Which `collections.OrderedDict` method moves an existing key to either end?

Accepted Answer

move_to_end()

Answer

move_to_front()

Answer

reorder()

Answer

shift()

Question 4

What does `namedtuple._fields` return for `Point = namedtuple('Point', 'x y')`?

Accepted Answer

('x', 'y')

Answer

{'x': 0, 'y': 1}

Answer

['x', 'y']

Answer

(0, 1)

Question 5

How does `collections.ChainMap` handle key lookups when the same key exists in multiple maps?

Accepted Answer

Returns the value from the first map where the key is found

Answer

Raises a DuplicateKeyError

Answer

Returns the value from the last map

Answer

Returns a list of all values

Question 6

What is the result of: `Counter([1,1,2,3]) + Counter([1,2,2])`?

Accepted Answer

Counter({1: 3, 2: 3, 3: 1})

Answer

Counter({1: 2, 2: 1, 3: 1})

Answer

Counter({1: 1, 2: 2, 3: 1})

Answer

Counter({2: 2, 1: 1})

Question 7

Which Python built-in can you use to convert a named tuple instance to a dictionary?

Accepted Answer

point._asdict()

Answer

dict(point)

Answer

point.to_dict()

Answer

vars(point)