zip and unzip
- Kotlin course
- Advanced
- Lesson 57/83
- 5 min
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.
Practice 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.
Starter code
// in main merge two lists with zip
// turn each pair into s=n and printSample solution
fun main() {
val pairs = listOf("a", "b", "c").zip(listOf(1, 2, 3)) { s, n -> "$s=$n" }
println(pairs)
}Expected output
[a=1, b=2, c=3]
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Match the zip/unzip parts
| Term | Meaning |
|---|---|
zip |
Parallel merge |
unzip |
Split into two lists |
Pair |
Element pair |
(a, 1) |
Result pair |
2 How many elements does listOf("a", "b").zip(listOf(1, 2, 3)) return?
- 1
- 5
- 3
- 2 Correct answer
Explanation: zip merges up to the shorter list's size.
3 Complete the unzip call
val (letters, nums) = listOf("a" to 1, "b" to 2).____()val (letters, nums) = listOf("a" to 1, "b" to 2).unzip()Explanation: unzip splits a Pair list into two lists.