Sequence vs collection performance in Kotlin - Interactive 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

BasSequence

Cmap

DtoList

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'toList()' which returns a list, not a sequence.

Using 'map()' or 'filter()' directly without converting to sequence first.

The asSequence() function converts a collection to a sequence for lazy operations.

2fill in blank

medium

Complete the code to get the first element greater than 3 from a sequence.

Kotlin

val seq = sequenceOf(1, 2, 3, 4, 5)
val first = seq.filter { it > 3 }.[1]()

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

Alast

Bmap

Cfind

Dfirst

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'last()' which returns the last element.

Using 'find()' which returns nullable and requires a predicate.

The first() function returns the first element matching the condition.

3fill in blank

hard

Fix the error in the code to sum numbers lazily using a sequence.

Kotlin

val numbers = listOf(1, 2, 3, 4, 5)
val sum = numbers.[1]().map { it * 2 }.sum()

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

AtoList

Bfilter

CasSequence

Dmap

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'toList()' which does not enable lazy evaluation.

Using 'map()' directly without converting to sequence.

Using asSequence() allows lazy evaluation before summing.

4fill in blank

hard

Fill both blanks to create a sequence and filter even numbers.

Kotlin

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

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

AasSequence

BtoList

Cfilter

Dmap

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'toList()' before filtering which is eager evaluation.

Using 'map' instead of 'filter' to select elements.

First convert to sequence with asSequence(), then filter even numbers with filter.

5fill in blank

hard

Fill all three blanks to create a sequence, map values, and find the max.

Kotlin

val numbers = listOf(1, 2, 3, 4, 5)
val maxVal = numbers.[1]().[2] { it * 3 }.[3]()

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

AasSequence

Bmap

Cmax

Dfilter

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'filter' instead of 'map' for transformation.

Using 'maxBy' which requires a selector function.

Not converting to sequence first.

Convert to sequence with asSequence(), map each value by multiplying by 3, then find the max with max().