advent-of-code-2019

4.scala

val candidates = Array.range(272091, 815432)
println("Initial digits: " + candidates.size)

val filteredAsc = candidates.map(_.toString.toArray).filter(a => a.sameElements(a.sortBy(_.toInt)))
println("Total digits with ascending order: " + filteredAsc.size)

val filteredDupOnly = filteredAsc.filter(a => a.toSet.size < a.size)
println("Total digits with at least 2 adjacent equal values: " + filteredDupOnly.size)

val filteredDoubleOnly = filteredDupOnly.map(_.groupBy(identity).view.mapValues(_.size)).filter(m => m.exists(_._2 == 2))
println("Total digits containing exactly two adjacent equal values: " + filteredDoubleOnly.size)