I have a List[(Int,Int)]
such that
{(1,5),(1,2),(1,7),(2,8),(2,3),(2,9),(3,10),(3,1),(3,12)}
What I want to do is to apply sum on every 2nd element of each (1,5),(1,2),(1,7)
2nd element of each (2,8),(2,3),(2,9)
and each (3,10),(3,1),(3,12)
such that we have a resultant:
List[Int]={14, 20, 23}
use grouped to split list by size, map the second value and sum, like:
list.grouped(3).map(_.map(_._2).sum).toList
> List(14, 20, 23)
You might group them by the 1st element of the tuple. Then you'll have a Map with a key for every distinct 1st element and a List of all the associated 2nd elements.
val myMap = myList.groupBy(_._1).mapValues(_.map(_._2))
Now you can sum the 2nd elements or apply any other transformation operation desired.
val mySums = myMap.mapValues(_.sum) //Map(2 -> 20, 1 -> 14, 3 -> 23)
And you can extract them in some desired order.
mySums.keys.toList.sorted.map(mySums) //res0: List[Int] = List(14, 20, 23)
