Array comparison and set operations in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code using array intersection?

Consider the following Ruby code snippet. What will it print?

Ruby

a = [1, 2, 3, 4]
b = [3, 4, 5, 6]
puts (a & b).inspect

A [5, 6]

B [1, 2, 3, 4, 5, 6]

C [3, 4]

D [1, 2]

💡 Hint

The & operator returns elements common to both arrays.

The & operator in Ruby returns a new array containing elements common to both arrays, without duplicates. Here, 3 and 4 are common.

❓ Predict Output

intermediate

What does this Ruby code print when using array difference?

Look at this Ruby code. What is the output?

Ruby

a = [1, 2, 3, 4]
b = [3, 4, 5, 6]
puts (a - b).inspect

A [1, 2]

B [3, 4]

C [1, 2, 3, 4, 5, 6]

D [5, 6]

💡 Hint

The - operator removes elements from the first array that appear in the second.

The - operator returns a new array with elements from the first array that are not in the second. So 3 and 4 are removed from a.

❓ Predict Output

advanced

What is the output of this Ruby code using array union?

What will this Ruby code print?

Ruby

a = [1, 2, 3]
b = [3, 4, 5]
puts (a | b).inspect

A [3, 4, 5]

B [1, 2, 3, 4, 5]

C [1, 2]

D [1, 2, 3, 3, 4, 5]

💡 Hint

The | operator returns all unique elements from both arrays.

The | operator returns a new array with unique elements from both arrays combined. Duplicates are removed.

❓ Predict Output

advanced

What error does this Ruby code raise when comparing arrays with a non-array?

What error will this Ruby code produce?

Ruby

a = [1, 2, 3]
b = 5
puts (b & a).inspect

A ArgumentError: wrong number of arguments (given 1, expected 0)

B TypeError: no implicit conversion of Integer into Enumerator

C TypeError: no implicit conversion of Integer into Array

D NoMethodError: undefined method `&' for Integer

💡 Hint

The & operator expects both operands to be arrays.

The & operator is defined for arrays. Using it with an Integer on the left causes NoMethodError because Integer does not have & method.

🧠 Conceptual

expert

How many unique elements are in the result of this Ruby array operation?

Given the arrays below, how many elements are in the array resulting from (a | b) - (a & b)?

Ruby

a = [1, 2, 3, 4, 5]
b = [4, 5, 6, 7]
result = (a | b) - (a & b)
puts result.size

A 5

B 4

C 6

D 7

💡 Hint

Think about the symmetric difference: elements in either array but not both.

The expression (a | b) - (a & b) gives the symmetric difference. Here, a | b is [1,2,3,4,5,6,7], a & b is [4,5]. Removing [4,5] leaves [1,2,3,6,7], which has 5 elements.