Why sequences matter for performance in Kotlin - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a list of numbers from 1 to 5.

Kotlin

val numbers = listOf([1])

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AlistOf(1, 2, 3, 4, 5)

B1..5

C1, 2, 3, 4, 5

DarrayOf(1, 2, 3, 4, 5)

Attempts:

3 left

💡 Hint

Common Mistakes

Using a range like 1..5 inside listOf creates a list with one element (the range), not the numbers.

Using arrayOf instead of listOf creates an array, not a list.

We use listOf with explicit values separated by commas to create a list.

2fill in blank

medium

Complete the code to convert a list to a sequence.

Kotlin

val seq = numbers.[1]()

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AasSequence

BtoSet

CtoList

Dmap

Attempts:

3 left

💡 Hint

Common Mistakes

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

Using map() requires a lambda and does not convert to sequence.

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

3fill in blank

hard

Fix the error in the code to filter even numbers using a sequence.

Kotlin

val evens = numbers.asSequence().filter { it [1] 2 == 0 }.toList()

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A%

B/

C*

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using division / instead of modulo %.

Using multiplication or addition operators which do not check divisibility.

The modulo operator % checks if a number is divisible by 2 (even).

4fill in blank

hard

Fill both blanks to create a sequence that maps numbers to their squares and then converts to a list.

Kotlin

val squares = numbers.[1]().[2] { it * it }.toList()

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AasSequence

Bmap

Cfilter

DtoList

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter instead of map to transform elements.

Using toList too early, before mapping.

First convert to a sequence with asSequence(), then use map to square each number.

5fill in blank

hard

Fill all three blanks to create a sequence that filters odd numbers, maps to double their value, and converts to a list.

Kotlin

val result = numbers.[1]().[2] { it % 2 != 0 }.[3] { it * 2 }.toList()

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

AasSequence

Bfilter

Cmap

DtoList

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up filter and map order.

Not converting to sequence before filtering and mapping.

Convert to sequence with asSequence(), filter odd numbers with filter, then double values with map.