20 lines
710 B
Scala
20 lines
710 B
Scala
object Amb {
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def amb(wss: List[List[String]]): Option[String] = {
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def _amb(ws: List[String], wss: List[List[String]]): Option[String] = wss match {
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case Nil => ((Some(ws.head): Option[String]) /: ws.tail)((a, w) => a match {
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case Some(x) => if (x.last == w.head) Some(x + " " + w) else None
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case None => None
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})
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case ws1 :: wss1 => ws1.flatMap(w => _amb(w :: ws, wss1)).headOption
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}
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_amb(Nil, wss.reverse)
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}
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def main(args: Array[String]) {
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println(amb(List(List("the", "that", "a"),
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List("frog", "elephant", "thing"),
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List("walked", "treaded", "grows"),
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List("slowly", "quickly"))))
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}
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}
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