Array operations (append, insert, remove) in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Swift code?

Consider the following Swift code that modifies an array. What will be printed?

Swift

var fruits = ["Apple", "Banana", "Cherry"]
fruits.append("Date")
fruits.insert("Elderberry", at: 1)
print(fruits)

A ["Apple", "Banana", "Elderberry", "Cherry", "Date"]

B ["Apple", "Elderberry", "Banana", "Cherry", "Date"]

C ["Apple", "Banana", "Cherry", "Date", "Elderberry"]

D ["Elderberry", "Apple", "Banana", "Cherry", "Date"]

💡 Hint

Remember that insert(at:) adds the element at the specified index, shifting others to the right.

The array starts as ["Apple", "Banana", "Cherry"]. append("Date") adds "Date" at the end. insert("Elderberry", at: 1) inserts "Elderberry" at index 1, pushing "Banana" and others right. So the final array is ["Apple", "Elderberry", "Banana", "Cherry", "Date"].

❓ Predict Output

intermediate

What happens after removing an element?

Given this Swift code, what will be the output?

Swift

var numbers = [10, 20, 30, 40, 50]
numbers.remove(at: 2)
print(numbers)

A [10, 20, 40, 50]

B [10, 20, 30, 40]

C [10, 30, 40, 50]

D [20, 30, 40, 50]

💡 Hint

Remember that remove(at:) removes the element at the given index and shifts the rest left.

The element at index 2 is 30. Removing it leaves [10, 20, 40, 50].

🔧 Debug

advanced

Why does this Swift code cause a runtime error?

Examine the code below. Why does it crash when run?

Swift

var letters = ["a", "b", "c"]
letters.remove(at: 3)
print(letters)

A It prints ["a", "b", "c"] without changes.

B It causes a compile-time error because remove(at:) is not a valid method.

C It causes a runtime error because index 3 is out of range for the array.

D It removes the last element "c" and prints ["a", "b"]

💡 Hint

Check the valid indices for the array before removing.

The array has indices 0, 1, 2. Trying to remove at index 3 causes a runtime 'index out of range' error.

❓ Predict Output

advanced

What is the final array after multiple operations?

What will be the output of this Swift code?

Swift

var colors = ["Red", "Green", "Blue"]
colors.insert("Yellow", at: 0)
colors.append("Purple")
colors.remove(at: 2)
print(colors)

A ["Yellow", "Red", "Blue", "Purple"]

B ["Yellow", "Red", "Green", "Purple"]

C ["Red", "Green", "Purple"]

D ["Yellow", "Green", "Blue", "Purple"]

💡 Hint

Track each operation step-by-step on the array.

Start: ["Red", "Green", "Blue"] Insert "Yellow" at 0: ["Yellow", "Red", "Green", "Blue"] Append "Purple": ["Yellow", "Red", "Green", "Blue", "Purple"] Remove at 2 ("Green"): ["Yellow", "Red", "Blue", "Purple"] Option A matches this exactly. So correct answer is B.

🧠 Conceptual

expert

How many elements remain after these operations?

Given this Swift code, how many elements are in the array after all operations?

Swift

var items = ["Pen", "Pencil", "Eraser", "Sharpener"]
items.append("Marker")
items.remove(at: 1)
items.insert("Notebook", at: 2)
items.removeLast()

A 6

B 5

C 3

D 4

💡 Hint

Count carefully after each operation.

Start with 4 elements. append("Marker") adds 1 → 5 elements. remove(at: 1) removes 1 → 4 elements. insert("Notebook", at: 2) adds 1 → 5 elements. removeLast() removes 1 → 4 elements remain.