zip and unzip

Learn combining with zip and unzip.

zip and unzip

zip merges two collections in parallel; each element becomes a Pair. unzip splits a list of Pairs into two lists.

Example: listOf("a", "b").zip(listOf(1, 2)) returns [(a, 1), (b, 2)]. listOf("a" to 1, "b" to 2).unzip() gives ([a, b], [1, 2]). zip merges up to the shorter list's size.

Transform with zip

Passing a lambda to zip transforms each pair. This is a concise way to relate two lists and produce a single list.

Example: listOf("a", "b").zip(listOf(1, 2)) { s, n -> "$s$n" }. This returns ["a1", "b2"]. The lambda takes two parameters: elements from the first and second list. This pattern is useful for joining label-value pairs.

Exercise Merge label and value with zip

In main assign the result of listOf("a", "b", "c").zip(listOf(1, 2, 3)) { s, n -> "$s=$n" } to a variable and print it with println.

Show example solution

fun main() {
    val pairs = listOf("a", "b", "c").zip(listOf(1, 2, 3)) { s, n -> "$s=$n" }
    println(pairs)
}

Test yourself

Match the zip/unzip parts

zip

Parallel merge
unzip

Split into two lists
Pair

Element pair
(a, 1)

Result pair
How many elements does listOf("a", "b").zip(listOf(1, 2, 3)) return?
- 1
- 5
- 3
- 2
Show answer

2 — zip merges up to the shorter list's size.

Complete the unzip call

val (letters, nums) = listOf("a" to 1, "b" to 2).____()

Show answer

val (letters, nums) = listOf("a" to 1, "b" to 2).unzip()

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