public class Perm {
   private static void reverse(int[] values, int first, int last){
      int temp;
      if(first == last)
          return;
      --last;
      while (first < last){
         // swap first, last
         temp = values[first];
         values[first] = values[last];
         values[last] = temp;

         ++first;
         --last;
      }
   }

   private static boolean nextPerm(int[] values){
        int i =  values.length - 1;

        if(values.length < 2)
            return false;

        for(;;) {
            int ii = i;
            --i;
            int temp;
            if (values[i] < values[ii]) {
                int j = values.length;
                while (values[i] >= values[--j]);

                // swap i, j
                temp = values[i];
                values[i] = values[j];
                values[j] = temp;

                reverse(values, ii, values.length);
                return true;
            }
            if (i == 0) {
                reverse(values, 0, values.length);
                return false;
            }
        }
    }


   public static void main(String[] args){
      int[] vals = {1,2,3,4,5, 6, 7 , 8 , 9, 10, 11, 12, 13};
     int count=0;
     do {
         count++;
     } while(nextPerm(vals));
     System.out.println("Found "+count+" Permutations");
   }

}