Sequence operators (map, filter) in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a sequence from a list.

Kotlin

val numbers = listOf(1, 2, 3, 4, 5)
val seq = numbers.[1]()

Drag options to blanks, or click blank then click option'

Afilter

Bmap

CasSequence

DtoList

Attempts:

3 left

💡 Hint

Common Mistakes

Using map or filter directly on the list without converting to sequence.

The asSequence() function converts a collection into a sequence, enabling lazy operations.

2fill in blank

medium

Complete the code to filter even numbers from the sequence.

Kotlin

val numbers = sequenceOf(1, 2, 3, 4, 5)
val evens = numbers.[1] { it % 2 == 0 }

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Afilter

BflatMap

Cmap

Dreduce

Attempts:

3 left

💡 Hint

Common Mistakes

Using map instead of filter, which transforms elements but does not select.

The filter function selects elements that satisfy the given condition, here even numbers.

3fill in blank

hard

Fix the error in the code to map numbers to their squares.

Kotlin

val numbers = sequenceOf(1, 2, 3)
val squares = numbers.[1] { it * it }

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Afilter

Bfold

Creduce

Dmap

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter which selects elements, not transforms them.

The map function transforms each element, here squaring each number.

4fill in blank

hard

Fill both blanks to create a sequence of squares of even numbers.

Kotlin

val numbers = listOf(1, 2, 3, 4, 5)
val result = numbers.asSequence().[1] { it % 2 == 0 }.[2] { it * it }.toList()

Drag options to blanks, or click blank then click option'

Afilter

Bmap

Creduce

Dfold

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping filter and map order, which changes the result.

First, filter selects even numbers, then map squares them.

5fill in blank

hard

Fill all three blanks to create a sequence of uppercase strings longer than 3 characters.

Kotlin

val words = listOf("cat", "dog", "elephant", "fox")
val result = words.asSequence().[1] { it.length > 3 }.[2] { it.[3]() }.toList()

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Afilter

Bmap

Cuppercase

Dlowercase

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase instead of uppercase.

Swapping filter and map order.

First, filter selects words longer than 3 letters, then map converts them to uppercase.