Swift Academy · Lesson

Set Operations: Union, Intersection, Difference

Performing mathematical set algebra and membership tests efficiently.

Lesson 3 of 412 steps

Set Operations: Union, Intersection, Difference is a free Swift Academy lesson on CoddyKit. This is lesson 3 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the Swift Academy learning path, and your progress syncs across the web and the CoddyKit app. The Swift Academy course includes 4 lessons in total.

Welcome

A `Set` stores unique, unordered values conforming to `Hashable`. It supports efficient mathematical set operations: union, intersection, difference, and more.

Creating Sets

```swift var fruits: Set = ["apple","banana","cherry"] var inferred: Set = [1, 2, 3, 3, 2] // {1,2,3} — duplicates removed ``` Sets are written like arrays but have type `Set`.

Membership Testing

```swift let primes: Set = [2,3,5,7,11] print(primes.contains(7)) // true — O(1) print(primes.contains(4)) // false ``` O(1) membership testing is Set's key advantage over Array's O(n).

Insert and Remove

```swift var colors: Set = ["red","green"] colors.insert("blue") // {"red","green","blue"} colors.remove("green") // {"red","blue"} let (inserted,_) = colors.insert("red") // inserted = false (already there) ```

Union

```swift let a: Set = [1,2,3] let b: Set = [3,4,5] print(a.union(b)) // {1,2,3,4,5} var c = a c.formUnion(b) // mutates c in-place ```

Intersection

```swift let a: Set = [1,2,3,4] let b: Set = [3,4,5,6] print(a.intersection(b)) // {3,4} print(a.isDisjoint(with: [7,8])) // true — no common elements ```

Subtracting (Difference)

```swift let all: Set = [1,2,3,4,5] let remove: Set = [2,4] let remaining = all.subtracting(remove) // {1,3,5} ```

Symmetric Difference

```swift let x: Set = [1,2,3] let y: Set = [2,3,4] print(x.symmetricDifference(y)) // {1,4} — elements in one but not both ```

Subset and Superset

```swift let small: Set = [1,2] let large: Set = [1,2,3,4] print(small.isSubset(of: large)) // true print(large.isSuperset(of: small)) // true print(small == large) // false ```

Converting Between Set and Array

```swift let arr = [1,2,2,3,3,3] let unique = Set(arr) // {1,2,3} let back = Array(unique).sorted() // [1,2,3] ``` Common pattern: dedup an array by round-tripping through Set.

Quick Check

Which Set operation returns only elements present in **both** sets?

Answer it in the interactive lesson

Recap

Key takeaways: • Sets store unique `Hashable` values with O(1) membership • `union`, `intersection`, `subtracting`, `symmetricDifference` • `isSubset`, `isSuperset`, `isDisjoint` • Dedup arrays: `Set(array)` then back to `Array` • Mutable variants: `formUnion`, `formIntersection`, etc. Next: choosing the right collection type.

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Frequently Asked Questions

Is the “Set Operations: Union, Intersection, Difference” lesson free?

Yes — any 3 lessons of the Swift Academy learning path, including “Set Operations: Union, Intersection, Difference”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The Swift Academy course includes 4 lessons in total.

What will I learn in “Set Operations: Union, Intersection, Difference”?

Performing mathematical set algebra and membership tests efficiently. You practise Swift Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Swift Academy?

No prior experience is required. Swift Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 3 of 4.

How long does the “Set Operations: Union, Intersection, Difference” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Swift Academy lesson?

Yes. Every Swift Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

Dictionary CRUD and Subscript Access
Iterating and Transforming Dictionaries
Set Operations: Union, Intersection, Difference
Choosing Between Array, Dictionary and Set

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