Suppose I have a sequence of integers and a number n < 30. How can I produce an array (of length n) that is 0 in all places except at the indices specified by the sequence (where it should be 1)?
For instance
Input:
Seq(1, 2, 5)
7
Output:
Array(0, 1, 1, 0, 0, 1, 0)
scala> val a = Array.fill(7)(0)
a: Array[Int] = Array(0, 0, 0, 0, 0, 0, 0)
scala> Seq(1,2,5).foreach(a(_) = 1)
scala> a
res1: Array[Int] = Array(0, 1, 1, 0, 0, 1, 0)
Alternatively,
scala> val is = Set(1, 2, 5)
is: scala.collection.immutable.Set[Int] = Set(1, 2, 5)
scala> Array.tabulate(10)(i => if (is contains i) 1 else 0)
res0: Array[Int] = Array(0, 1, 1, 0, 0, 1, 0, 0, 0, 0)
is(i) if you can afford the parens.def makeArray(indices: Seq[Int], size: Int): Array[Int] = Iterable.tabulate(size) {
case idx if indices contains idx => 1
case _ => 0
}.toArray
makeArray(Seq(1, 2, 5), size = 7)
