julythree.scala

import cats.data.State
import cats.instances.vector._
import scala.language.higherKinds
import cats.syntax.applicative._

object julythree {

  def main(args: Array[String]): Unit = {

    val ins = List(List('0', '1'), List('A', 'B', 'C'), List('D', 'E', 'F', 'G'))
    val ins2 = List(List('0', '1', '2', '3'), List('A', 'B', 'C', 'D'), List('E', 'F', 'G', 'H', 'I'))
    val ins3= List(List('0', '1', '2', '3', '4'),
      List('A', 'B', 'C', 'D', 'E'),
      List('F', 'G', 'H', 'I'),
      List('J', 'K', 'L'))

    val list_pairs = ins3.foldLeft(List(List[Any]()))( (acc,next) =>
      if (acc.isEmpty) {
        next.map(List(_))
      } else {
        acc.flatMap( e => next.map( x => {x :: e})
    )}).map(_.reverse)

    type pairState[A] = State[Set[Any],A]

    def check(curr: List[Any],l:List[Any]): pairState[List[Any]] =
      State[Set[Any],List[Any]]{ seen => {
        val pairs = l.sliding(2).toSet
        val c = pairs.map( (e) => seen.contains(e)).reduce(_&&_)
        val f = if(c) List() else l
        (pairs ++ seen,curr ++ List(f))
      }}

    val r = scala.util.Random.shuffle(list_pairs).foldLeft( List[Any]().pure[pairState])( (m,next) => {
     m.flatMap( x => check(x,next) )
    })

    val filtered_list = r.run(Set()).value._2.filter( _ match {
        case  _ :: _ => true
        case _ => false
      }
    )

    filtered_list.foreach(a => println(a))
    println(filtered_list.length)

  }

}