CODEWITHSUNDEEP
scalasortingfunctional-programming
Valentin
Valentin

Reputation: 149

Sort a collection of values based on another collection in a "Scala way"

I have to sort a collection of values depending on a set of keys I have available as sublists of another list. Currently, I have the following code which does the job properly. However, it uses a mutable collection and I know this is not the best way to do this in Scala. What would be the pretty "Scala way" of doing this ? Thanks.

var sorted: IndexedSeq[IndexedSeq[Any]]
//sortKeys is a list of lists containing sorting properties (index,descending/ascending) 
for (i <- (0 until sortKeys).reverse) {
      val index = sortKeys(i).get(i).getIndex
      val desc = sortKeys.get(i).descending
      if (desc) {
        sorted = sorted.sorted { (t1: IndexedSeq, t2: IndexedSeq) => -t1(index).asInstanceOf[Comparable[Any]].compareTo(t2(index)) }
      } else {
        sorted = sorted.sorted { (t1: IndexedSeq, t2: IndexedSeq) => t1(index).asInstanceOf[Comparable[Any]].compareTo(t2(index)) }
      }
    }

Upvotes: 0

Views: 281

Answers (1)

Thilo
Thilo

Reputation: 262494

Rough sketch:

val sortKeys = Seq( (1,true), (2, false))

val input = Seq( Array("a", "b", "c"), Array("a", "x", "c" )

sortKeys.foldRight(input){
  case ( (index, ascending), acc) =>
     acc.sortWith( (a,b) => if (ascending) a(index) > b(index)    
          else a(index) < b(index))
}

Upvotes: 2

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