import java.util.*; public class VoodooPrime { public static void main(String[] args) { System.out.println ("This is the Kiuziu's Voodoo-Primes Solution"); System.out.println ("Enter two integers, for example: 3 and 0 if you want to test the 3 on Voodoo Prime"); System.out.println ("For example, enter two integers: 2 and 200. If you want to test the range for voodoo primes\n"); // change maxDigits for more or less decimal places. int maxDigits = 350; // user input section Scanner sc = new Scanner(System.in); int firstNumber = sc.nextInt(); int secondNumber = sc.nextInt(); sc.close(); if (secondNumber == 0) System.out.println(firstNumber + " is a Voodoo-Prime? " + (isVoodooPrime(firstNumber, maxDigits) ? "Yes" : "No")); else { if(firstNumber > secondNumber) { int t = firstNumber; firstNumber = secondNumber; secondNumber = t; } // puts out the Voodoo-Prime-Numbers and Reciprocal of the Voodoo-Prime-Numbers for (int i = firstNumber; i < secondNumber; i++) { if (isPrime(i) && isVoodooPrime(i, maxDigits)) { String text = "the Voodoo-Prime-Number is %s. The Reciprocal %s%n"; System.out.printf(text, i, divid(1, i, maxDigits)); } } } } public static boolean isPeriodicalFraction(int denominator) { ArrayList a = PFZ(denominator); for(int i = 0; i < a.size(); i++) { if(a.get(i) != 2 && a.get(i) != 5) return true; } return false; } /* * if the number a Voodoo-Prime-Number returns true otherwise false */ public static boolean isVoodooPrime(int number, int maxDigits) { String numberReciprocal = divid(1, number, maxDigits); String n = "" + number; return numberReciprocal.contains(n); } /** * The Integer Factorial method with such many decimal places are you want * The result are not rounded. * @param numerator * @param denominator * @param maxDigits many decimal places are you want * @return the result is a Decimal Number as a String */ public static String divid(int numerator, int denominator, int maxDigits) { if(denominator == 0) throw new ArithmeticException("division by zero not allowed."); if(numerator == 0) return "0"; int z = numerator; int n = denominator; int count = 0; String fraction = ""; do { int x = z / n; fraction += "" + x; if(!fraction.contains(".")) fraction += "."; z = z % n; if(z == numerator && count > 0) return computeNiceResult(fraction, denominator); if (z == 0) return computeNiceResult(fraction, denominator); z *= 10; } while (count++ < maxDigits); return computeNiceResult(fraction, denominator); } private static String computeNiceResult(String fraction, int denominator) { if(fraction.endsWith(".")) return fraction.substring(0, fraction.length()-1); if(isPeriodicalFraction(denominator)) return fraction + " period"; return fraction; } /** * isPrime(number) return true if number is a prime-number * @param number * @return true if prime else false */ public static boolean isPrime(long number) { if (number == 2 || number == 3) return true; if (number % 2 == 0 || number < 2) return false; long sqrt = (long) Math.sqrt(number) + 1; for (long i = 3; i < sqrt; i += 2) if (number % i == 0) return false; return true; } /** * PFZ is meaning "Prime-Factor-Separation" * @param n the number to analysis * @return an Array of the Prime Factors of n */ public static ArrayList PFZ(long n) { ArrayList result = new ArrayList<>(); long N = n; long i = 2; while(i <= N) { if(isPrime(i) && N % i == 0) { result.add(i); N /= i; } else i++; } return result; } }

my Solution of the Voodoo-Prime-Challenge