Swift Set
🔢 Swift Set (Advanced & Operations) – Deep Dive for Interviews & Real Projects
This guide covers advanced Swift Set concepts and operations that are frequently asked in interviews and used in real-world apps.
1️⃣ What is a Set in Swift? (Quick Recap)
A Set is an unordered collection of unique elements.
Output:
📌 Duplicate values are automatically removed.
2️⃣ Set Initialization – Advanced Ways ⭐
3️⃣ Mutability (var vs let) ⭐⭐
4️⃣ Core Set Operations ⭐⭐⭐ (VERY IMPORTANT)
Assume:
🔹 Union
Output:
🔹 Intersection
Output:
🔹 Subtracting (Difference)
Output:
🔹 Symmetric Difference
Output:
5️⃣ Relationship Operations ⭐⭐⭐
📌 Used for set logic checks.
6️⃣ Insert, Remove & Update ⭐⭐
7️⃣ Fast Membership Test ⭐⭐
📌 Much faster than arrays for lookup.
8️⃣ Looping Through Set ⭐⭐
📌 Order is not guaranteed.
9️⃣ Set vs Array vs Dictionary ⭐⭐⭐
| Feature | Set | Array | Dictionary |
|---|---|---|---|
| Unique elements | ✅ | ❌ | Keys only |
| Ordered | ❌ | ✅ | ❌ |
| Fast lookup | ✅ | ❌ | ✅ |
| Index-based access | ❌ | ✅ | ❌ |
🔟 Convert Between Collections ⭐⭐
Set → Array
Array → Set
1️⃣1️⃣ Set with Custom Types ⭐⭐⭐
📌 Hashable is required.
1️⃣2️⃣ Performance & Internals ⭐⭐⭐
-
Set is a value type
-
Uses hashing
-
Implements Copy-on-Write (CoW)
1️⃣3️⃣ Common Mistakes ❌
❌ Expecting ordered output
❌ Using Set when duplicates matter
❌ Forgetting Hashable for custom types
❌ Modifying Set during iteration
📌 Interview Questions (Swift Set – Advanced)
Q1. Why is Set faster than Array?
👉 Hash-based lookup
Q2. What is symmetric difference?
👉 Elements in either set, not both
Q3. Can Set store custom objects?
👉 Yes, if they conform to Hashable
Q4. When to use Set instead of Array?
👉 When uniqueness & fast lookup are required
✅ Summary
✔ Set stores unique values
✔ Unordered but fast
✔ Supports union, intersection, difference
✔ Requires Hashable
✔ Copy-on-Write improves performance
✔ Very important for Swift interviews
