import Foundation

func vampire<T>(n: T) -> [(T, T)] where T: BinaryInteger, T.Stride: SignedInteger {
  let strN = String(n).sorted()
  let fangLength = strN.count / 2
  let start = T(pow(10, Double(fangLength - 1)))
  let end = T(Double(n).squareRoot())

  var fangs = [(T, T)]()

  for i in start...end where n % i == 0 {
    let quot = n / i

    guard i % 10 != 0 || quot % 10 != 0 else {
      continue
    }

    if "\(i)\(quot)".sorted() == strN {
      fangs.append((i, quot))
    }
  }

  return fangs
}

var count = 0
var i = 1.0

while count < 25 {
  let start = Int(pow(10, i))
  let end = start * 10

  for num in start...end {
    let fangs = vampire(n: num)

    guard !fangs.isEmpty else { continue }

    count += 1

    print("\(num) is a vampire number with fangs: \(fangs)")

    guard count != 25 else { break }
  }

  i += 2
}

for (vamp, fangs) in [16758243290880, 24959017348650, 14593825548650].lazy.map({ ($0, vampire(n: $0)) }) {
  if fangs.isEmpty {
    print("\(vamp) is not a vampire number")
  } else {
    print("\(vamp) is a vampire number with fangs: \(fangs)")
  }
}