Set algebra (union, intersection, difference) in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Swift code using set union?

Consider two sets of integers. What will be printed after performing a union?

Swift

let setA: Set<Int> = [1, 2, 3]
let setB: Set<Int> = [3, 4, 5]
let unionSet = setA.union(setB)
print(unionSet.sorted())

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

B [1, 2, 4, 5]

C [3]

D [1, 2, 3]

💡 Hint

Union combines all unique elements from both sets.

The union of two sets contains all elements from both sets without duplicates. Here, 3 is common, so it appears once.

❓ Predict Output

intermediate

What is the output of this Swift code using set intersection?

Find the common elements between two sets.

Swift

let setX: Set<Int> = [10, 20, 30, 40]
let setY: Set<Int> = [30, 40, 50, 60]
let intersectionSet = setX.intersection(setY)
print(intersectionSet.sorted())

A [30, 40]

B [10, 20, 30, 40, 50, 60]

C [50, 60]

D [10, 20]

💡 Hint

Intersection returns only elements present in both sets.

Only 30 and 40 are in both setX and setY, so the intersection is {30, 40}.

❓ Predict Output

advanced

What is the output of this Swift code using set difference?

Find elements in the first set that are not in the second set.

Swift

let setM: Set<Int> = [5, 10, 15, 20]
let setN: Set<Int> = [10, 20, 30]
let differenceSet = setM.subtracting(setN)
print(differenceSet.sorted())

A [30]

B [10, 20]

C [5, 15]

D [5, 10, 15, 20, 30]

💡 Hint

Difference removes elements of the second set from the first set.

Elements 10 and 20 are removed from setM because they appear in setN. Leftover are 5 and 15.

🧠 Conceptual

advanced

Which Swift set operation returns elements that are in either set but not in both?

Choose the correct set operation that returns elements exclusive to each set, excluding common elements.

A intersection(_:)

B symmetricDifference(_:)

C union(_:)

D subtracting(_:)

💡 Hint

Think about elements that are unique to each set, not shared.

symmetricDifference returns elements that are in one set or the other but not both, unlike union or intersection.

❓ Predict Output

expert

What is the output of this Swift code combining multiple set operations?

Analyze the combined set operations and determine the final printed array.

Swift

let a: Set<Int> = [1, 2, 3, 4]
let b: Set<Int> = [3, 4, 5, 6]
let c: Set<Int> = [4, 5, 6, 7]
let result = a.union(b).intersection(c).subtracting([7])
print(result.sorted())

A [1, 2, 3]

B [3, 4]

C [5, 6, 7]

D [4, 5, 6]

💡 Hint

Break down the operations step-by-step: union, then intersection, then subtracting.

First, a.union(b) = {1,2,3,4,5,6}. Then intersect with c = {4,5,6,7} gives {4,5,6}. Finally, subtract 7 leaves {4,5,6}.