Swift Multidimensional Arrays

🍎 Swift Multidimensional Arrays – Complete Tutorial

A multidimensional array in Swift is an array of arrays.
They are commonly used for tables, matrices, grids, game boards, and UI layouts.

1️⃣ What is a Multidimensional Array?

• An array that contains other arrays

• Most common type: 2D Array

📌 Here, matrix is a 2D array (rows × columns).

2️⃣ Creating Multidimensional Arrays ⭐

2D Array (Int)

2D Array (String)

3️⃣ Accessing Elements ⭐

Syntax:

⚠️ Index out of range → runtime crash

4️⃣ Looping Through a 2D Array ⭐⭐

Nested for-in Loop (Most Common)

Loop with Row & Column Index

✔ Safe
✔ Interview-friendly

5️⃣ Modifying Multidimensional Arrays ⭐

Update Value

Append New Row

Append to Existing Row

6️⃣ Creating Empty 2D Array ⭐

7️⃣ Fixed Size Matrix Initialization ⭐⭐

📌 Very common interview question

8️⃣ Jagged Arrays (Uneven Rows) ⭐

Swift allows rows of different lengths.

✔ Flexible
❌ Be careful with indexing

9️⃣ Bounds Safety in Multidimensional Arrays ⭐

Always check indices.

✔ Prevents crashes

🔟 Multidimensional Arrays vs Dictionaries ⭐

1️⃣1️⃣ Common Mistakes ❌

❌ Index out of range
❌ Assuming equal row sizes
❌ Using [Int][Int] (wrong syntax)
❌ Forgetting nested loops

📌 Interview Questions & MCQs

Q1. What is a 2D array in Swift?

A) Array of values
B) Dictionary
C) Array of arrays
D) Tuple

✅ Answer: C

Q2. Correct access syntax?

A) arr[row, col]
B) arr[row][col]
C) arr[row-col]
D) arr(row)(col)

✅ Answer: B

Q3. How to initialize 3×3 matrix with zeros?

A) Loop only
B) Array(repeating:)
C) Dictionary
D) Set

✅ Answer: B

Q4. Does Swift allow jagged arrays?

A) Yes
B) No

✅ Answer: A

Q5. What happens if index is out of range?

A) Returns nil
B) Compile error
C) Runtime crash
D) Ignored

✅ Answer: C

🔥 Real-Life Use Cases

✔ Game boards (chess, tic-tac-toe)
✔ Grid layouts
✔ Matrix calculations
✔ Seating charts
✔ Image pixel data

✅ Summary

• Multidimensional arrays = arrays of arrays

• Access using [row][column]

• Use nested loops

• Swift supports jagged arrays

• Initialize fixed-size matrices with Array(repeating:)

• Always handle bounds safely

• Very important for Swift interviews & app logic