CODEWITHSUNDEEP
scala
ZZZ
ZZZ

Reputation: 955

Using groupBy on a List of Tuples in Scala

I tried to group a list of tuples in Scala.

The input:

val a = List((1,"a"), (2,"b"), (3,"c"), (1,"A"), (2,"B"))

I applied:

a.groupBy(e => e._1)

The output I get is:

Map[Int,List[(Int, String)]] = Map(2 -> List((2,b), (2,B)), 1 -> List((1,a), (1,A)), 3 -> List((3,c)))

This is slightly different with what I expect:

Map[Int,List[(Int, String)]] = Map(2 -> List(b, B), 1 -> List(a, A)), 3 -> List(c))

What can I do to get the expected output?

Upvotes: 4

Views: 2781

Answers (2)

Srinivas Katta
Srinivas Katta

Reputation: 35

If you do not want to use mapValues, is this what you are expecting?

 a.groupBy(_._1).map(f => (f._1, f._2.map(_._2)))

Result

Map(2 -> List(b, B), 1 -> List(a, A), 3 -> List(c))

Upvotes: 0

Andrey Tyukin
Andrey Tyukin

Reputation: 44977

You probably meant something like this:

a.groupBy(_._1).mapValues(_.map(_._2))

or:

a.groupBy(_._1).mapValues(_.unzip._2)

Result:

Map(2 -> List(b, B), 1 -> List(a, A), 3 -> List(c))

Upvotes: 4

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