List(34,12,14,23), "11" -> List(22,11,34)) I just can't seem ...">
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Sort list within a map in scala

I have a map like:

val v = Map("01" -> List(34,12,14,23), "11" -> List(22,11,34))

I just can't seem to find a way to sort the list items within the map.

I tried:

v.flatMap(v => v._2.sortBy(list => list._))

but it seems like it doesn't sort the list items.

Does anyone know where I am going wrong?

UPDATE : Actually my list is a list of tuples of type List[(Object1, Object2, Object3, Object4)]

I put in int

for simplicity. (but I think that _.sorted

won't work for my object). So I basically want to sort by one of the columns of these objects. (for example Object1.int

)

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2 answers


It works:

v.mapValues(_.sorted)
// Map(01 -> List(12, 14, 23, 34), 11 -> List(11, 22, 34))

If your values ​​are tuples, try this:

v.mapValues(_.sortBy(_._1))

This approach will also work for classes, just say for example. _.sortBy(_.age)

...



Or if you want one, concatenated list:

v.values.flatten.toSeq.sorted
// List(11, 12, 14, 22, 23, 34, 34)

(for a list of tuples):

v.values.flatten.toSeq.sortBy(_._1)
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Do you mean this?

val v = Map("01" -> List(34,12,14,23), "11" -> List(22,11,34))
//v: scala.collection.immutable.Map[String,List[Int]] = Map(01 -> List(34, 12, 14, 23), 11 -> List(22, 11, 34))

v map { case (k, v) => (k -> v.sorted) }
//res0: scala.collection.immutable.Map[String,List[Int]] = Map(01 -> List(12, 14, 23, 34), 11 -> List(11, 22, 34))

Change or:

v mapValues (_ sorted)
//res1: scala.collection.immutable.Map[String,List[Int]] = Map(01 -> List(12, 14, 23, 34), 11 -> List(11, 22, 34))

Another edit:



If there is an implicit one Ordering

for all types in your tuples, it should work exactly the same:

val v = Map(
  "01" -> List((34, "thirty-four"), (12, "twelve"), (14, "fourteen"), (23, "twenty-three")), 
  "11" -> List((22, "twenty-two"), (11, "eleven"), (34, "thirty-four")))
//v: scala.collection.immutable.Map[String,List[(Int, String)]] =
//Map(
//  01 -> List((34,thirty-four), (12,twelve), (14,fourteen), (23,twenty-three)), 
//  11 -> List((22,twenty-two), (11,eleven), (34,thirty-four)))

v mapValues (_ sorted)
//res3: scala.collection.immutable.Map[String,List[(Int, String)]] =
//Map(
//  01 -> List((12,twelve), (14,fourteen), (23,twenty-three), (34,thirty-four)),
//  11 -> List((11,eleven), (22,twenty-two), (34,thirty-four)))

If you only want to sort one member of a tuple (say ... the second in this case):

v mapValues (_ sortBy (_ _2))
//res5: scala.collection.immutable.Map[String,List[(Int, String)]] =
//Map(
//  01 -> List((14,fourteen), (34,thirty-four), (12,twelve), (23,twenty-three)),
//  11 -> List((11,eleven), (34,thirty-four), (22,twenty-two)))
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