How can I find the n! permutations of certain letters on Scala?
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问题:
回答1:
Scala 2.9 RC1:
scala> "abc".permutations.toList
res58: List[String] = List(abc, acb, bac, bca, cab, cba)
回答2:
scala> def permutations[T](xs: List[T]): List[List[T]] = xs match {
| case Nil => List(Nil)
| case _ => for(x <- xs;ys <- permutations(xs diff List(x))) yield x::ys
| }
permutations: [T](xs: List[T])List[List[T]]
scala> permutations("abc".toList) foreach println
List(a, b, c)
List(a, c, b)
List(b, a, c)
List(b, c, a)
List(c, a, b)
List(c, b, a)
