Sets

Question 1

What is a set in data structures?

Answer 1

A collection of unique elements with no specific order.

Question 2

What is the key property of a set?

Answer 2

It does not allow duplicate elements.

Question 3

What are common operations on a set?

Answer 3

Insert, delete, search, union, intersection, difference.

Question 4

What is the time complexity of insert in a hash set?

Answer 4

O(1) average case.

Question 5

What is the time complexity of search in a hash set?

Answer 5

O(1) average case.

Question 6

What is the time complexity of delete in a hash set?

Answer 6

O(1) average case.

Question 7

What is a hash set?

Answer 7

A set implemented using a hash table.

Question 8

What is a tree set?

Answer 8

A set implemented using a balanced binary search tree.

Question 9

What is the time complexity of operations in a tree set?

Answer 9

O(log n).

Question 10

What is a subset?

Answer 10

A set where all elements are contained in another set.

Question 11

What is a superset?

Answer 11

A set that contains all elements of another set.

Question 12

What is the union of two sets?

Answer 12

A set containing all distinct elements from both sets.

Question 13

What is the intersection of two sets?

Answer 13

A set containing only elements present in both sets.

Question 14

What is the difference of two sets?

Answer 14

A set containing elements in the first set but not in the second.

Question 15

How do you check if an element is in a set?

Answer 15

Use the contains or ‘in’ operator depending on the language.

Question 16

What is the space complexity of a set?

Answer 16

O(n), where n is the number of elements.

Question 17

What is the benefit of using a set over a list?

Answer 17

Faster lookups and guaranteed uniqueness.

Question 18

What is a multiset?

Answer 18

A collection that allows duplicate elements.

Question 19

What is the main disadvantage of sets?

Answer 19

They do not maintain insertion order (in hash sets).

Question 20

What is an ordered set?

Answer 20

A set that maintains elements in sorted or insertion order.

Question 21

What happens if you try to insert a duplicate into a set?

Answer 21

The duplicate is ignored.

Question 22

What is the mathematical definition of a set?

Answer 22

A well-defined collection of distinct objects.

Question 23

How do you iterate through a set?

Answer 23

Using a for-loop or an iterator.

Question 24

What is a power set?

Answer 24

The set of all subsets of a given set.

Question 25

What is the size of the power set of a set with n elements?

Answer 25

2^n.

Question 26

Can sets contain other sets?

Answer 26

Yes, if the inner sets are immutable (hashable).

Question 27

How is a set different from a dictionary?

Answer 27

A set stores only keys; a dictionary stores key-value pairs.

Question 28

How do you remove an element from a set?

Answer 28

Use the remove or discard method.

Question 29

What is the difference between remove and discard?

Answer 29

Remove raises an error if the item is missing; discard does not.

Question 30

What is a frozen set?

Answer 30

An immutable version of a set.

Question 31

How do sets help in finding duplicates?

Answer 31

By checking if an element already exists before adding.

Question 32

What is a use case for sets in string manipulation?

Answer 32

Finding unique characters in a string.

Question 33

How do you compute the symmetric difference of two sets?

Answer 33

Elements in either set, but not both.

Question 34

What is the result of intersecting a set with an empty set?

Answer 34

An empty set.

Question 35

What is the result of the union of a set and an empty set?

Answer 35

The original set.

Question 36

Are sets ordered in Python?

Answer 36

No, but since Python 3.7, insertion order is preserved in practice.

Question 37

Can sets be used as dictionary keys?

Answer 37

No, but frozen sets can.

Question 38

What is the advantage of sets in graph problems?

Answer 38

Efficient membership checks for visited nodes.

Question 39

Can a set be null?

Answer 39

No, it can be empty but not null.

Question 40

What is the syntax to create a set in Python?

Answer 40

Use set() or curly braces: {1, 2, 3}.

Question 41

How do you clear all elements from a set?

Answer 41

Use the clear() method.

Question 42

What is the use of sets in database operations?

Answer 42

To perform union, intersection, and difference on result sets.

Question 43

Can you convert a list to a set?

Answer 43

Yes, using set(list_name).

Question 44

How do sets handle collisions?

Answer 44

Via the underlying hash function and collision resolution of the hash table.

Question 45

What is the expected time complexity of checking membership in a set?

Answer 45

O(1) on average.

Question 46

What data structure underlies a hash set?

Answer 46

A hash table.

Question 47

What is the cardinality of a set?

Answer 47

The number of elements in the set.

Question 48

Are set operations associative?

Answer 48

Yes, operations like union and intersection are associative.