CODEWITHSUNDEEP
scala
Sparker0i
Sparker0i

Reputation: 1851

Foreach on the first element of list

I have a list of tuples, where each tuple is of type (String, String).

A sample list can be: List((A,B), (A,C), (A,D), (A,E), (B,C), (B,A), (B,D), (B,E), (C,A), (C,B), (C,D), (C,E),...).

I want to do two things on this list:

I'm not able to figure out the logic for both of them combined, because if we do Random.shuffle() and then a .take(), it might take in any given order, not necessarily 3 for each of the first element.

Upvotes: 1

Views: 200

Answers (2)

Luis Miguel Mejía Suárez
Luis Miguel Mejía Suárez

Reputation: 22850

If I understand you correctly, you want something like this:

def pickNRandomByKey[K : Ordering, V](n: Int)(data: List[(K, V)]): List[(K, List[V])] =
  data
    .groupMap(_._1)(_._2)
    .view
    .mapValues(group => Random.shuffle(group).take(n))
    .toList
    .sortBy(_._1)

Upvotes: 3

user
user

Reputation: 7604

You can first group by the first element, shuffle the inner lists, and then extract 3 tuples from those lists and flatten at the end 

list.groupBy(_._1).map { case (k, v) => Random.shuffle(v).take(3) }.flatten

Output will look something like:

List((A,C), (A,B), (A,E), (B,A), (B,C), (B,E), (C,E), (C,D), (C,A), (D,C), (D,A), (D,B) ...)

Upvotes: 3

Related Questions