CODEWITHSUNDEEP
scala
WelcomeTo
WelcomeTo

Reputation: 20591

Scala: Split array into chunks by some logic

Is there some predefined function in Scala to split list into several lists by some logic? I found grouped method, but it doesn't fit my needs.

For example, I have List of strings: List("questions", "tags", "users", "badges", "unanswered").

And I want to split this list by max length of strings (for example 12). In other words in each resulting chunk sum of the length of all strings should not be more than 12: 

List("questions"), List("tags", "users"), List("badges"), List("unanswered")

EDIT: I'm not necessarily need to find the most optimal way of combining strings into chunks, just linear loop which checks next string in list, and if its length doesn't fit to required (12) then return current chunk and next string will belong to next chunk

Upvotes: 1

Views: 3939

Answers (2)

jbrown
jbrown

Reputation: 7996

If you can make reasonable assumptions about the max length of a string (e.g. 10 characters), you could then use sliding which is much faster for a long list:

val elementsPerChunk = ???   // do some maths like 
                             // CHUNK_SIZE / MAX_ELEM_LENGTH
val test = List("questions", "tags", "users", "badges", "unanswered")
test.sliding(elementsPerChunk, elementsPerChunk).toList

Upvotes: 1

Sascha Kolberg
Sascha Kolberg

Reputation: 7162

There is no buildIn mechanism to do that, that I know of, but you could achieve something like that with a foldLeft and bit of coding:

val test = List("questions", "tags", "users", "badges", "unanswered")

test.foldLeft(List.empty[List[String]]) {
  case ((head :: tail), word) if head.map(_.length).sum + word.length < 12 =>
    (word :: head) :: tail
  case (result, word) =>
    List(word) :: result
}

-> res0: List[List[String]] = List(List(unanswered), List(badges), List(users, tags), List(questions))

Upvotes: 7

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