Filter and filterNot in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to filter even numbers from the list.

Kotlin

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

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

A%

B*

C/

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using division (/) instead of modulo (%) causes wrong filtering.

Using multiplication (*) or addition (+) operators here is incorrect.

The filter function keeps elements where the condition is true. Using % 2 == 0 selects even numbers.

2fill in blank

medium

Complete the code to filter out odd numbers using filterNot.

Kotlin

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

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

A-

B*

C+

D%

Attempts:

3 left

💡 Hint

Common Mistakes

Using multiplication or addition operators instead of modulo.

Confusing filter and filterNot logic.

The filterNot function excludes elements where the condition is true. Using % 2 != 0 excludes odd numbers, keeping evens.

3fill in blank

hard

Fix the error in the code to filter words longer than 3 characters.

Kotlin

val words = listOf("cat", "dog", "elephant", "fox")
val longWords = words.filter { it.length [1] 3 }
println(longWords)

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

A<=

B>

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using less than (<) instead of greater than (>).

Using equality (==) which only selects words of length exactly 3.

To get words longer than 3 characters, use > operator comparing length to 3.

4fill in blank

hard

Fill both blanks to create a map of word lengths for words shorter than 5 characters.

Kotlin

val words = listOf("apple", "bat", "cat", "dog", "elephant")
val shortWordLengths = words.filter { it.length [1] 5 }.associateWith { it.[2] }
println(shortWordLengths)

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

A<

Blength

C>

DtoString

Attempts:

3 left

💡 Hint

Common Mistakes

Using greater than (>) instead of less than (<) in filter.

Using toString instead of length for mapping.

Filter words with length less than 5 using <. Then map each word to its length using length.

5fill in blank

hard

Fill all three blanks to create a map of uppercase words to their lengths for words not starting with 'a'.

Kotlin

val words = listOf("apple", "bat", "cat", "dog", "ant")
val result = words.filterNot { it.startsWith([1]) }.associateWith { it.[2] }.mapKeys { it.key.[3]() }
println(result)

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

A"a"

Blength

Cuppercase

DtoUpperCase

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase instead of toUpperCase() function.

Forgetting quotes around "a" in startsWith.

Using wrong property for length.

Filter out words starting with "a" using startsWith("a"). Map values to their length. Change keys to uppercase using toUpperCase().