superpermutations

main.swift

let max = 15

var len = 0
var counts = [Int](repeating: 0, count: max)
var pos = 0

func factSum(n: Int) -> Int {
  var s = 0
  var x = 0
  var f = 1

  while x < n {
    x += 1
    f *= x
    s += f
  }

  return s
}

func r(n: Int) -> Bool {
  guard n != 0 else {
    return false
  }

  counts[n] -= 1

  if counts[n] == 0 {
    counts[n] = n

    if !r(n: n - 1) {
      return false
    }
  }

  pos += 1

  return true
}

func superPermutations(n: Int) {
  guard n != 0 else {
    return
  }

  pos = n
  len = factSum(n: n)

  for i in 0...n {
    counts[i] = i
  }

  while r(n: n) {}
}

for i in 0..<max {
  superPermutations(n: i)
  print("superPerm(\(i)) = \(len)")
}