Combinations polygots

combinations.txt

// Ruby

[-15,10,4,-3,5,-7,1,-5].reduce([[]]) {|ll, l| ll + ll.map{|a| a + [l]}}.select{|l| l.inject(:+) == 0}

// (Scala (functions)

List(-15,10,4,-3,5,-7,1,-5).foldLeft(List(List[Int]())){ (ll,l) => ll ++ ll.map{l :: _}}.filter(!_.isEmpty).filter(_.sum == 0)

// Scala (recursion)

def combi[A](l : List[A]) : List[List[A]] = {
  def _combi(k : List[A], ll : List[List[A]]) : List[List[A]] = {
    if (k.isEmpty) ll
    else _combi(k.tail, __combi(k.head, ll, ll))
  }

  def __combi(a : A, la : List[List[A]], result : List[List[A]]) : List[List[A]] = {
    if (la.isEmpty) result
    else __combi(a, la.tail, (a :: la.head) ::  result)
  }

  _combi(l, List(List.empty[A]))
}

combi(List(1,2,3))
combi(List(1,2,3,4,5)).size

// Clojure
(reduce (fn [x y] (into x (map (fn [z] (cons  y z)) x))) '(()) '(1 2 3 1)) 
(count (reduce (fn [x y] (into x (map (fn [z] (cons  y z)) x))) '(()) '(1 2 3 1)))