recursive.java

// ---------------------------------------------------------------------
// The Great Computer Language Shootout
// http://shootout.alioth.debian.org/
//
// Code based on / inspired by existing, relevant Shootout submissions
//
// Contributed by Anthony Borla
// ---------------------------------------------------------------------

public class recursive
{
  public static void main(String args[])
  {
    int n = Integer.parseInt(args[0]);

    System.out.printf("Ack(3,%d): %d\n", n, ack(3, n));
    System.out.printf("Fib(%.1f): %.1f\n", 27.0 + n, fib(27.0 + n));

    n -= 1;
    System.out.printf("Tak(%d,%d,%d): %d\n", n * 3, n * 2, n, tak(n * 3, n * 2, n));

    System.out.printf("Fib(3): %d\n", fib(3));
    System.out.printf("Tak(3.0,2.0,1.0): %.1f\n", tak(3.0, 2.0, 1.0));
  }

  public static int ack(int m, int n)
  {
    if (m == 0) return n + 1;
    if (n == 0) return ack(m - 1, 1);
    return ack(m - 1, ack(m, n - 1));
  }

  public static int fib(int n)
  {
    if (n < 2) return 1;
    return fib(n - 2) + fib(n - 1);
  }

  public static double fib(double n)
  {
    if (n < 2.0) return 1.0;
    return fib(n - 2.0) + fib(n - 1.0);
  }

  public static int tak(int x, int y, int z)
  {
    if (y >= x) return z;
    return tak(tak(x - 1, y, z), tak(y - 1, z, x), tak(z - 1, x, y));
  }

  public static double tak(double x, double y, double z)
  {
    if (y >= x) return z;
    return tak(tak(x - 1.0, y, z), tak(y - 1.0, z, x), tak(z - 1.0, x, y));
  }
}