// Some methods that demonstrate recursion

public class Recursion
{
   public static void main( String args[] )
   {
      System.out.println( factorial( 5 ) );
      System.out.println( power( 8, 4 ) );
      int list[] = { 1,3,8,2,9,6 };
      reverseArray( list, 0, 5 );
      for( int i = 0; i < 6; i++ )
         System.out.print( list[i] + " " );
      System.out.println();
   }

   public static int factorial( int n )
   {
      if ( n == 0 )
         return 1;
      else
         return n * factorial( n - 1 );
   }

   public static int power( int x, int n )
   {
      if ( n == 0 )
         return 1;
      if ( n % 2 == 1 )
      {
         int y = power( x, n/2 );
         return x*y*y;
      }
      else
      {
         int y = power( x, n/2 );
         return y*y;
      }
   }

   public static void reverseArray( int S[], int i, int j )
   {
      if ( i < j )
      {
         // swap S[i] and S[j]
         int temp = S[i];
         S[i] = S[j];
         S[j] = temp;
         reverseArray( S, i+1, j-1 );
      }
   }
}