Hackerrank - HackerRank Python Collections and Data Structures Questions and Answers

Question 1

A developer is processing a large log file where each line contains a user's action.
They need to count the occurrences of each unique action to identify the most common ones.
Which Python collection is the most efficient and idiomatic for this task?

Accepted Answer

A `collections.Counter` object.

Answer

A dictionary, manually incrementing counts for each action.

Answer

A list of tuples, where each tuple stores an action and its count.

Answer

A set to store the unique actions, then iterating through it to count them in the original file.

Question 2

What is the output of the following Python code snippet?

```python
set_a = {1, 2, 3, 4, 5}
set_b = {4, 5, 6, 7, 8}
result = set_a.symmetric_difference(set_b)
print(sorted(list(result)))
```

Accepted Answer

[1, 2, 3, 6, 7, 8]

Answer

[4, 5]

Answer

[1, 2, 3, 4, 5, 6, 7, 8]

Answer

[1, 2, 3]

Question 3

You are creating a data structure to hold the configuration settings for an application. These settings are defined once at startup and should never be changed during the program's execution to prevent accidental modification. Which of the following data structures is the most appropriate choice?

Accepted Answer

A tuple, because it is immutable and ordered.

Answer

A dictionary, because it allows for named settings.

Answer

A list, because it maintains the order of settings.

Answer

A frozenset, because it is immutable.

Question 4

A programmer is building an index to group a list of words by their first letter. If a letter has not been seen before, a new list should be created for it. Which of the following is the most suitable and efficient approach to initialize the index?

Accepted Answer

A `collections.defaultdict(list)`.

Answer

A standard `dict`, checking for the key's existence with an `if` statement on each iteration.

Answer

A `collections.OrderedDict` to maintain the order of letters.

Answer

A list of lists, where the index corresponds to the letter's position in the alphabet.

Question 5

Which of the following statements about the `collections.deque` object in Python is true?

Accepted Answer

It provides O(1) time complexity for append and pop operations from both ends.

Answer

It provides O(n) performance for appends and pops from both ends.

Answer

It is immutable and cannot be changed after creation.

Answer

It is optimized for fast random access to elements in the middle of the sequence.

Question 6

You need to store a collection of unique, hashable items where the order of elements does not matter, and you need to perform fast membership testing (i.e., checking if an item is in the collection). Which data structure should you use?

Accepted Answer

A `set`

Answer

A `list`

Answer

A `tuple`

Answer

A `dict`

A developer is processing a large log file where each line contains a user's action.They need to count the occurrences of each unique action to identify the most common ones.Which Python collection is the most efficient and idiomatic for this task?

A developer is processing a large log file where each line contains a user's action.
They need to count the occurrences of each unique action to identify the most common ones.
Which Python collection is the most efficient and idiomatic for this task?