Hackerrank Collections and Data Structures 2

Question 1

What does `collections.OrderedDict` guarantee that a regular `dict` does NOT guarantee in Python versions before 3.7?

Accepted Answer

Insertion order preservation

Answer

Key uniqueness

Answer

O(1) lookup time

Answer

Thread safety

Question 2

Which method of `collections.deque` removes and returns an element from the LEFT end?

Accepted Answer

popleft()

Answer

pop()

Answer

remove()

Answer

shift()

Question 3

What is the output of: `from collections import Counter; c = Counter('aabbc'); print(c.most_common(2))`?

Accepted Answer

[('a', 2), ('b', 2)]

Answer

[('a', 2), ('b', 2), ('c', 1)]

Answer

{'a': 2, 'b': 2}

Answer

[('c', 1), ('b', 2)]

Question 4

What happens when you access a missing key in a `collections.defaultdict(list)`?

Accepted Answer

Creates an entry with an empty list

Answer

Raises KeyError

Answer

Returns None

Answer

Creates an entry with value 0

Question 5

Which named tuple method returns a new instance replacing specified fields with new values?

Accepted Answer

_replace()

Answer

_update()

Answer

_modify()

Answer

_set()

Question 6

What is the time complexity of `collections.deque.appendleft()`?

Accepted Answer

O(1)

Answer

O(n)

Answer

O(log n)

Answer

O(n log n)

Question 7

How do you create a named tuple class called `Point` with fields `x` and `y`?

Accepted Answer

Point = namedtuple('Point', ['x', 'y'])

Answer

Point = namedtuple(['x', 'y'])

Answer

Point = NamedTuple('Point', x, y)

Answer

Point = tuple.named('Point', 'x y')