// From: Matthew Gorle <ma901mg@mcs.gold.ac.uk>
// Date: Wed, 23 Oct 2002 23:07:37 +0100

/*

  Solutions to CIS-212 Lab 3

  23-10-02, Matthew Gorle

  Notes: o All programming problems are solved recursively and iteratively.
         o All solutions (except recursive fibonacci) by MG.
         o The "Recompiles" field in comments refers to the number of
           logical errors that needed to be fixed.  On average, one
           error is fixed per recompile.  Your Mileage May Vary!!
         o The solution used in the iterativeFibonacci method is, I think,
           too complicated.  If you want to punish yourself, see if you can
           find another way of doing it.

  What?!  No comments??!  That's just how I write my code.  In my opinion,
  descriptive method/variable names are equally, if not more, important.

                                                  --MG (22:49. 23-10-02)
  
*/

class Lab3
{
   int recursiveFactorial(int x)
      /*
        Time spent on solution : <1 minute
        Recompiles             : 0
        Unsolved Issues        : 0
        Gave up after          : N/A
      */
   {
      if (x>1)
         return x*recursiveFactorial(x-1);
      else
         return 1;
   }

   int iterativeFactorial(int x)
      /*
        Time spent on solution : <1 minute
        Recompiles             : 0
        Unsolved Issues        : 0
        Gave up after          : N/A
      */
   {
      int y=1;
      for(int i=1;i<=x;i++)
         y*=i;
      return y;
   }
   
   String recursiveReverse(String x)
      /*
        Time spent on solution : 3 minutes
        Recompiles             : 1
        Unsolved Issues        : 0
        Gave up after          : N/A
      */
   {
      if (x.length()>0)
         return (recursiveReverse(x.substring(1))+x.charAt(0));
      else
         return "";
   }

   String iterativeReverse(String x)
      /*
        Time spent on solution : 1 minute
        Recompiles             : 0
        Unsolved Issues        : 0
        Gave up after          : N/A
      */
   {
      String y="";
      for (int i=x.length();i>0;i--)
      {
         y+=""+x.charAt(i-1);
      }
      return y;
   }  
   
   int recursiveFibonacci(int x)
      /*
        Time spent on solution : N/A
        Recompiles             : 3
        Unsolved Issues        : 1
        Gave up after          : 15 minutes                      
           (looked at Ida's solution)
      */
   {
      if (x>2)
         return recursiveFibonacci(x-2)+recursiveFibonacci(x-1);
      else
         return 1;
   }

   int iterativeFibonacci(int x)
      /*
        Time spent on solution : 6 minutes
        Recompiles             : 4
        Unsolved Issues        : 0
        Gave up after          : N/A
      */
   {
      int y=1;
      int z=1;
      int a=y;
      for(int i=2;i<x;i++)
      {
         a = y + z;
         if (i%2==1)
            y = a;
         else
            z = a;
      }
      return a;
   }

   public static void main(String[] args)
   {
      Lab3 l3 = new Lab3();
      System.out.println("recursiveFactorial(5) = "+l3.recursiveFactorial(5));
      System.out.println("iterativeFactorial(5) = "+l3.iterativeFactorial(5));
      System.out.println("recursiveReverse(\"Reverse!\") = "+
                         l3.recursiveReverse("Reverse!"));
      System.out.println("iterativeReverse(\"Reverse!\") = "+
                         l3.iterativeReverse("Reverse!"));
      System.out.println("recursiveFibonacci(4) = "+l3.recursiveFibonacci(4));
      System.out.println("iterativeFibonacci(4) = "+l3.iterativeFibonacci(4));
   }
}