Zip for combining collections in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the zip function do in Kotlin?

The zip function combines two collections into a single list of pairs, where each pair contains elements from the same position in both collections.

beginner

How does Kotlin handle collections of different sizes when using zip?

Kotlin stops zipping when the shortest collection ends, so the resulting list has the size of the smaller collection.

beginner

Show a simple example of using zip with two lists in Kotlin.

Example:<br>

val numbers = listOf(1, 2, 3)
val words = listOf("one", "two", "three")
val zipped = numbers.zip(words)
// zipped = [(1, "one"), (2, "two"), (3, "three")]

intermediate

Can you customize the output of zip in Kotlin?

Yes, you can provide a transform function to zip that defines how to combine elements instead of returning pairs.

intermediate

What is the output of this Kotlin code?<br>

val a = listOf(1, 2)
val b = listOf("A", "B", "C")
val result = a.zip(b) { num, str -> "$num$str" }

The output is a list: ["1A", "2B"]. The zip stops at the shortest list length (2), and combines elements using the transform function.

What does Kotlin's zip function return when combining two lists?

A A list of elements only from the longer list

B A single list containing all elements from both lists

C A map with keys from the first list and values from the second

D A list of pairs combining elements from both lists

The zip function pairs elements from both lists into a list of pairs.

If one list has 3 elements and the other has 5, how many pairs does zip produce?

A 5

B 8

C 3

D 0

Zipping stops at the shortest list length, so it produces 3 pairs.

How can you customize the output of zip in Kotlin?

A By passing a transform function to combine elements

B By changing the list sizes before zipping

C By using <code>map</code> after <code>zip</code>

D By converting lists to arrays first

You can provide a transform function to zip to define how elements combine.

What is the type of the result when you call zip without a transform function?

A List<Pair<T, R>>

B List<T>

C List<R>

D Map<T, R>

Without a transform, zip returns a list of pairs combining elements.

Which of these is a valid use of zip in Kotlin?

A val zipped = zip(list1, list2)

B val zipped = list1.zip(list2) { a, b -> a + b }

C val zipped = list1.zip()

D val zipped = list1.zip(list2).toMap()

Option B uses zip with a transform function correctly.

Explain how the zip function works in Kotlin and what happens when the collections have different sizes.

Think about pairing elements from two lists like matching socks.

Describe how to customize the output of zip in Kotlin using a transform function.

Imagine mixing ingredients to create a new recipe instead of just pairing them.