Partition for splitting in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to split the list into two lists based on a condition.

Kotlin

val numbers = listOf(1, 2, 3, 4, 5)
val (even, odd) = numbers.partition { it [1] 2 == 0 }

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

A%

Bmod

Cdiv

Drem

Attempts:

3 left

💡 Hint

Common Mistakes

Using division operator instead of modulo

Using incorrect operator like 'mod' which is not valid syntax

The '%' operator is used to get the remainder, so 'it % 2 == 0' checks if a number is even.

2fill in blank

medium

Complete the code to partition words by length greater than 3.

Kotlin

val words = listOf("cat", "house", "dog", "elephant")
val (longWords, shortWords) = words.partition { it.length [1] 3 }

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

A<

B<=

C==

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' which selects shorter words

Using '==' which selects words exactly length 3

We want words longer than 3, so the condition is 'it.length > 3'.

3fill in blank

hard

Fix the error in the partition condition to split numbers divisible by 3.

Kotlin

val nums = listOf(3, 4, 6, 7, 9)
val (divByThree, others) = nums.partition { it [1] 3 == 0 }

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

Amod

B%

C/

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using division '/' instead of modulo

Using multiplication '*' which is incorrect

The modulo operator '%' checks divisibility by 3 correctly.

4fill in blank

hard

Fill both blanks to partition a list of strings into those starting with 'a' and others.

Kotlin

val fruits = listOf("apple", "banana", "avocado", "cherry")
val (aFruits, otherFruits) = fruits.partition { it[1].startsWith([2]) }

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

A.

B->

C"a"

D'a'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '->' instead of '.'

Using single quotes for string literal

Use '.' to call the method and double quotes for string literal "a".

5fill in blank

hard

Fill all three blanks to partition a list of integers into positives and non-positives.

Kotlin

val numbers = listOf(-1, 0, 2, 3, -5)
val (positive, nonPositive) = numbers.partition { it [1] [2] 0 [3] }

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

A>

B>=

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' which selects negatives

Using '==' which selects only zero

The condition 'it > 0' selects positives; 'it >= 0' and 'it == 0' are common comparisons but only 'it > 0' is needed here.

Practice

1. What does the partition function do in Kotlin when applied to a list?

easy

A. Converts the list into a map with indices as keys.

B. Sorts the list in ascending order.

C. Removes duplicate elements from the list.

D. Splits the list into two lists based on a condition, returning a Pair of lists.

Solution

1. Step 1: Understand the purpose of partition

   The partition function divides a list into two parts based on a condition.

2. Step 2: Recognize the return type

   It returns a Pair where the first list contains elements matching the condition, and the second list contains the rest.

3. Final Answer:

   Splits the list into two lists based on a condition, returning a Pair of lists. -> Option D

4. Quick Check:

   partition = split by condition [OK]

Hint: Remember: partition always returns two lists in a Pair [OK]

Common Mistakes:

• Thinking partition sorts the list
• Confusing partition with filtering
• Assuming partition removes duplicates

2. Which of the following is the correct syntax to use partition on a list numbers to split even and odd numbers?

easy

A. val (evens, odds) = numbers.partition { it % 2 == 0 }

B. val (evens, odds) = numbers.partition(it % 2 == 0)

C. val evens = numbers.partition { it % 2 == 0 }

D. val evens, odds = numbers.partition { it % 2 == 0 }

Solution

1. Step 1: Check the lambda syntax inside partition

   The condition must be inside curly braces with it representing each element.

2. Step 2: Verify destructuring declaration

   Partition returns a Pair, so use val (first, second) = ... to get both lists.

3. Final Answer:

   val (evens, odds) = numbers.partition { it % 2 == 0 } -> Option A

4. Quick Check:

   Correct lambda and destructuring = val (evens, odds) = numbers.partition { it % 2 == 0 } [OK]

Hint: Use val (a, b) = list.partition { condition } [OK]

Common Mistakes:

• Missing curly braces for lambda
• Not using destructuring for Pair
• Using parentheses instead of braces for lambda

3. What is the output of this Kotlin code?

val words = listOf("apple", "banana", "avocado", "berry")
val (aWords, otherWords) = words.partition { it.startsWith('a') }
println(aWords)
println(otherWords)

medium

A. ["apple", "avocado"]
["banana", "berry"]

B. ["banana", "berry"]
["apple", "avocado"]

C. ["apple"]
["banana", "avocado", "berry"]

D. ["avocado"]
["apple", "banana", "berry"]

Solution

1. Step 1: Apply the condition to each word

   Check which words start with 'a': "apple" and "avocado" match.

2. Step 2: Partition splits into two lists

   First list has words starting with 'a', second list has the rest: "banana", "berry".

3. Final Answer:

   ["apple", "avocado"] ["banana", "berry"] -> Option A

4. Quick Check:

   partition by startsWith('a') = ["apple", "avocado"] ["banana", "berry"] [OK]

Hint: Check condition on each element carefully [OK]

Common Mistakes:

• Mixing order of lists in output
• Forgetting that partition returns Pair of lists
• Confusing startsWith with contains

4. Identify the error in this Kotlin code using partition:

val nums = listOf(1, 2, 3, 4)
val evens, odds = nums.partition { it % 2 == 0 }
println(evens)
println(odds)

medium

A. partition cannot be used on lists of integers.

B. The lambda condition is incorrect; should be it % 2 != 0.

C. Missing parentheses around evens and odds for destructuring declaration.

D. println statements are missing string interpolation.

Solution

1. Step 1: Check destructuring declaration syntax

   Destructuring a Pair requires parentheses: val (evens, odds) = ....

2. Step 2: Confirm lambda and usage

   The lambda is correct for evens; partition works on lists of integers; println is fine.

3. Final Answer:

   Missing parentheses around evens and odds for destructuring declaration. -> Option C

4. Quick Check:

   Destructuring needs parentheses [OK]

Hint: Use val (a, b) = ... for destructuring Pair [OK]

Common Mistakes:

• Omitting parentheses in destructuring
• Changing correct lambda unnecessarily
• Thinking partition only works on strings

5. Given a list of mixed integers including zero and negatives, how can you use partition to separate positive numbers from zero and negatives? Choose the correct code snippet.

hard

A. val (positives, nonPositives) = numbers.partition { it < 0 }

B. val (positives, nonPositives) = numbers.partition { it > 0 }

C. val (positives, nonPositives) = numbers.partition { it >= 0 }

D. val (positives, nonPositives) = numbers.partition { it == 0 }

Solution

1. Step 1: Define the condition for positives

   Positive numbers are greater than zero, so condition is it > 0.

2. Step 2: Use partition with this condition

   Partition splits list into positives and the rest (zero and negatives).

3. Final Answer:

   val (positives, nonPositives) = numbers.partition { it > 0 } -> Option B

4. Quick Check:

   Partition by it > 0 separates positives [OK]

Hint: Use it > 0 to get positives, rest are zero/negatives [OK]

Common Mistakes:

• Using it >= 0 includes zero as positive
• Using it < 0 reverses groups
• Using it == 0 only selects zeros