MCQs on Collections in Ruby | Ruby

Explore the power of Ruby collections with MCQs covering Arrays, Hashes, and common methods. Understand creation, manipulation, iteration, and key-value pair usage for better programming practices.

---

Topic 1: Arrays – Creation, Manipulation, and Iteration

1. How do you create an empty array in Ruby?
   a) array = []
   b) array = {}
   c) array = ()
   d) array = new Array()
2. Which method is used to add an element to the end of an array in Ruby?
   a) append
   b) push
   c) insert
   d) add
3. How can you access the third element of an array arr = [10, 20, 30, 40] in Ruby?
   a) arr[2]
   b) arr[3]
   c) arr(3)
   d) arr[1]
4. Which of the following methods removes the last element from an array?
   a) pop
   b) shift
   c) slice
   d) delete
5. What does the map method do when applied to an array?
   a) Modifies the array in place
   b) Creates a new array based on the original array’s elements
   c) Deletes elements from the array
   d) Reverses the array
6. How do you iterate over each element in an array in Ruby?
   a) for x in array
   b) array.each { |element| ... }
   c) array.each { element in ... }
   d) array.each()
7. How do you remove nil values from an array?
   a) array.remove_nil
   b) array.compact
   c) array.filter_nil
   d) array.delete_nil
8. How do you join an array of strings into a single string?
   a) array.join(", ")
   b) array.concat(", ")
   c) array.merge(", ")
   d) array.combine(", ")
9. What method would you use to find the length of an array in Ruby?
   a) array.size
   b) array.length
   c) array.count
   d) All of the above
10. What does the reverse method do to an array in Ruby?
    a) Reverses the order of elements
    b) Removes the last element
    c) Creates a new array
    d) Sorts the array in reverse order

---

Topic 2: Hashes – Key-Value Pairs and Usage

11. How do you create a hash in Ruby with keys and values?
    a) hash = {key1 => value1, key2 => value2}
    b) hash = [key1, value1, key2, value2]
    c) hash = (key1, value1, key2, value2)
    d) hash = Hash.new(key1: value1)
12. Which method retrieves the value associated with a given key in a hash?
    a) get
    b) fetch
    c) access
    d) retrieve
13. How do you add a new key-value pair to an existing hash?
    a) hash.add(key, value)
    b) hash[key] = value
    c) hash.insert(key, value)
    d) hash.push(key, value)
14. What method is used to remove a key-value pair from a hash?
    a) remove
    b) delete
    c) pop
    d) clear
15. How do you iterate over a hash in Ruby?
    a) for key, value in hash
    b) hash.each { |key, value| ... }
    c) hash.each_pair { |key, value| ... }
    d) All of the above
16. Which of the following methods will return an array of keys in a hash?
    a) hash.keys
    b) hash.get_keys
    c) hash.to_a
    d) hash.values
17. How do you check if a key exists in a hash?
    a) hash.has_key?(key)
    b) hash.contains?(key)
    c) hash.key?(key)
    d) Both a and c
18. Which method is used to merge two hashes in Ruby?
    a) merge
    b) combine
    c) union
    d) concat
19. How can you obtain the value of a hash key, but return a default value if the key doesn’t exist?
    a) hash[key] || default_value
    b) hash.fetch(key, default_value)
    c) hash.get(key, default_value)
    d) Both a and b
20. What is the method to retrieve all values from a hash?
    a) hash.values
    b) hash.get_values
    c) hash.value
    d) hash.find_values

---

Topic 3: Common Methods for Arrays and Hashes

21. What method can you use to check if an array contains a specific element?
    a) array.include?(element)
    b) array.has?(element)
    c) array.exists?(element)
    d) array.contains?(element)
22. Which method is used to find the index of a specific element in an array?
    a) array.find_index(element)
    b) array.index_of(element)
    c) array.locate(element)
    d) array.get_index(element)
23. Which method returns a new array with elements sorted in ascending order?
    a) array.sort
    b) array.ascending
    c) array.order
    d) array.sort_by
24. How do you check if a hash is empty in Ruby?
    a) hash.empty?
    b) hash.is_empty?
    c) hash.null?
    d) hash.clear?
25. What does the flatten method do in Ruby?
    a) Combines nested arrays into a single array
    b) Removes duplicate elements from the array
    c) Converts all elements into strings
    d) Sorts the array in place
26. How do you find the size of a hash in Ruby?
    a) hash.size
    b) hash.count
    c) hash.length
    d) All of the above
27. How can you remove all elements from an array in Ruby?
    a) array.remove_all
    b) array.clear
    c) array.delete_all
    d) array.empty
28. Which method would you use to combine multiple arrays in Ruby?
    a) concat
    b) merge
    c) combine
    d) append
29. How do you convert a hash to an array of key-value pairs?
    a) hash.to_a
    b) hash.arrayize
    c) hash.keys_values
    d) hash.to_array
30. Which method is used to check if an element exists in a hash?
    a) hash.include?(key)
    b) hash.exists?(key)
    c) hash.contains?(key)
    d) hash.has_key?(key)

---

Answers Table

QNo	Answer
1	a) array = []
2	b) push
3	a) arr[2]
4	a) pop
5	b) Creates a new array based on the original array’s elements
6	b) `array.each {
7	b) array.compact
8	a) array.join(", ")
9	d) All of the above
10	a) Reverses the order of elements
11	a) hash = {key1 => value1, key2 => value2}
12	b) fetch
13	b) hash[key] = value
14	b) delete
15	d) All of the above
16	a) hash.keys
17	d) Both a and c
18	a) merge
19	d) Both a and b
20	a) hash.values
21	a) array.include?(element)
22	a) array.find_index(element)
23	a) array.sort
24	a) hash.empty?
25	a) Combines nested arrays into a single array
26	d) All of the above
27	b) array.clear
28	a) concat
29	a) hash.to_a
30	d) hash.has_key?(key)