Question

I’m trying to work through Udacity’s CS212 using Scala but had trouble with the Zebra Puzzle,

Some of the concepts in python just doesn’t convert to Scala easily, especially for a beginner like me.

These are the codes I’ve managed so far,

  val houses = List(1, 2, 3, 4, 5)
  val orderings = houses.permutations

  def imright(h1: Int, h2: Int): Boolean = {
    if (h1 - h2 == 1) true
    else false
  }

  def nextto(h1: Int, h2: Int): Boolean = {
    if (math.abs(h1 - h2) == 1) true
    else false
  }

the houses = [first, _, middle, _. _] = [1, 2, 3, 4, 5] stumped me.
Furthermore, how do i express the for (red, green, ivory, yellow, blue) in orderings in Scala? Please help me, thanks.

Answer 1

You want

val houses = List(1, 2, 3, 4, 5)
val List(first, _, middle, _, _) = houses

and

for (List(red, green, ivory, yellow, blue) <- orderings)

respectively. Also, note that in Scala these sorts of destructurings must be assigned to variables starting with a lower-case letter; upper-case indicates that it is instead supposed to match an existing variable (or throw an exception if it does not!).