如何使用scala組合字符串中的值？

Question

我想結合字符串中的值。 例如，

Let A = a,b,c,d 

我想要的組合，

AComb = a,b,c,d,ab,ac,ad,bc,bd,cd,abc,abd,bcd,acd 

Answer 1

我假設A是Set

scala> val A =Set("a","b","c","d") 
A: scala.collection.immutable.Set[String] = Set(a, b, c, d) 


scala> val AComb=A.toSet[String].subsets.map(_.mkString).toVector 
AComb: Vector[String] = Vector("", a, b, c, d, ab, ac, ad, bc, bd, cd, abc, abd, acd, bcd, abcd) 

我在想，你並不需要首先元素，所以你可以試試

scala> val AComb=A.toSet[String].subsets.map(_.mkString).toVector.tail 
AComb: scala.collection.immutable.Vector[String] = Vector(a, b, c, d, ab, ac, ad, bc, bd, cd, abc, abd, acd, bcd, abcd) 

除去第一和最後的元件

scala> val AComb=A.toSet[String].subsets.map(_.mkString).toVector.init.tail 
AComb: scala.collection.immutable.Vector[String] = Vector(a, b, c, d, ab, ac, ad, bc, bd, cd, abc, abd, acd, bcd) 

根據評

scala> val xc1=Set("sunny","hot","high","FALSE","no") 
xc1: scala.collection.immutable.Set[String] = Set(sunny, FALSE, hot, no, high) 

scala> val AComb=xc1.toSet[String].subsets.map(_.mkString(" ")).toVector.tail; 
AComb: scala.collection.immutable.Vector[String] = Vector(sunny, FALSE, hot, no, high, sunny FALSE, sunny hot, sunny no, sunny high, FALSE hot, FALSE no, FALSE high, hot no, hot high, no high, sunny FALSE hot, sunny FALSE no, sunny FALSE high, sunny hot no, sunny hot high, sunny no high, FALSE hot no, FALSE hot high, FALSE no high, hot no high, sunny FALSE hot no, sunny FALSE hot high, sunny FALSE no high, sunny hot no high, FALSE hot no high)