pattern.scala

// https://www.codewars.com/kata/complete-the-pattern-number-13/python
object Pattern {

  def spaces(size: Int) = Seq.fill(size)(" ").mkString

  // line is 0-indexed
  def pattern(n: Int, xArg: Int = 1, line: Int = 0, acc: Seq[String] = Seq[String]()): String = {
    val x = if(xArg <= 1) 1 else xArg
    if(line < n) {
      val numToPrint = (line + 1) % 10
      // spacing 'inside' and 'outside' each V
      val innerSpacing = 1 + ((n - line - 2) * 2)
      val outerSpacing = spaces(line * 2 - 1)
      val lineOutput = if(line == 0) {
        Seq.fill(x + 1)(numToPrint).mkString(spaces(innerSpacing))
      } else {
        val vContent = if(line == n - 1) numToPrint else numToPrint.toString + spaces(innerSpacing) + numToPrint.toString
        spaces(line) + Seq.fill(x)(vContent).mkString(outerSpacing)
      }
      pattern(n, x, line + 1,  acc :+ lineOutput)
    } else {
      // mirror image of V's creates the X's
      (acc ++ acc.dropRight(1).reverse).mkString("\n")
    }
  }

  def main(args: Array[String]) = {
    println(pattern(0))
    println(pattern(4, 3))
    println(pattern(10, 2))
    println(pattern(25))
    println(pattern(3, -1))
  }
}