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Swift Academy · Lesson

Set Operations: Union, Intersection, Difference

Performing mathematical set algebra and membership tests efficiently.

Set Operations: Union, Intersection, Difference is a free Swift Academy lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Swift Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

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?

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.

Frequently asked questions

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

Yes — the full text of “Set Operations: Union, Intersection, Difference” is free to read here on the web, and the Swift Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Swift Academy course, upgrade to CoddyKit PRO.

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; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.

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

  1. Dictionary CRUD and Subscript Access
  2. Iterating and Transforming Dictionaries
  3. Set Operations: Union, Intersection, Difference
  4. Choosing Between Array, Dictionary and Set
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