Collection slicing and indices in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get a slice of the array from index 1 to 3.

Swift

let numbers = [10, 20, 30, 40, 50]
let slice = numbers[[1]]

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A1...3

B0...2

C3...5

D2...4

Attempts:

3 left

💡 Hint

Common Mistakes

Using a range that starts at 0 instead of 1.

Using an open range operator which excludes the last index.

The slice 1...3 gets elements at indices 1, 2, and 3.

2fill in blank

medium

Complete the code to get the first three elements of the array using prefix.

Swift

let fruits = ["apple", "banana", "cherry", "date"]
let firstThree = fruits.[1](3)

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Asuffix

BdropLast

CdropFirst

Dprefix

Attempts:

3 left

💡 Hint

Common Mistakes

Using suffix instead of prefix.

Using dropFirst which removes elements instead of selecting.

The prefix(3) method returns the first three elements of the collection.

3fill in blank

hard

Fix the error in the code to correctly get a slice from index 2 to the end.

Swift

let letters = ["a", "b", "c", "d", "e"]
let slice = letters[[1]...]

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A2

B3

Cletters.startIndex

Dletters.endIndex

Attempts:

3 left

💡 Hint

Common Mistakes

Using endIndex which is one past the last valid index.

Using startIndex which gets the whole array.

Using 2... gets the slice from index 2 to the end.

4fill in blank

hard

Fill both blanks to create a slice of the array from index 1 up to but not including index 4.

Swift

let colors = ["red", "green", "blue", "yellow", "purple"]
let slice = colors[[1]..<[2]]

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A1

B3

C4

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using a closed range which includes index 4.

Using wrong start or end indices.

The half-open range 1..<4 includes indices 1, 2, and 3.

5fill in blank

hard

Fill all three blanks to create a dictionary with keys as uppercase letters and values as their index, only for letters with index greater than 1.

Swift

let letters = ["a", "b", "c", "d", "e"]
let dict = [[1]: [2] for (index, letter) in letters.enumerated() if index [3] 1]

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Aletter.uppercased()

Bindex

C>

Dletter

Attempts:

3 left

💡 Hint

Common Mistakes

Using the letter itself instead of uppercase for keys.

Using wrong comparison operator in the condition.

This comprehension creates a dictionary where keys are uppercase letters and values are their indices, only for indices greater than 1.