Question

I have a map like:

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

I simply can’t find a way to sort the list items within map.

I tried like:

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

but seems that it does not sort list items.

Does anybody know where I am wrong?

UPDATE: Actually my List are List of tuples like List[(Object1, Object2, Object3, Object4)], I put int for simplicity. (but I think _.sorted will not work for my objects case). So I basically want to sort by one of this objects column. (for instance Object1.int)

Answer 1

This seems to work:

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 e.g. _.sortBy(_.age).

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Or if you want one, merged list:

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

(for list of tuples):

v.values.flatten.toSeq.sortBy(_._1)