//这是原代码，进行填空

 public class    Main{

     public static String remain(int[] a)

     {

         String s = "";

         for(int i=0; i<a.length; i++){

             if(a[i] == 0) s += (char)(i+'A');

         }

         return s;

     }  

     public static void f(String s, int[] a)

     {

         for(int i=0; i<a.length; i++){

             if(a[i]==1) continue;

             a[i] = 1;

             for(int j=i+1; j<a.length; j++){

                 if(a[j]==1) continue;

                 a[j]=1;

                 for(int k=j+1; k<a.length; k++){

                     if(a[k]==1) continue;

                     a[k]=1;

                     //此处应填 s+" "+(char)(i+'A')+(char)(j+'A')+(char)(k+'A')+" "+remain(a)

                     System.out.println( s+" "+(char)(i+'A')+(char)(j+'A')+(char)(k+'A')+" "+remain(a));  //填空位置

                     a[k]=0;

                 }

                 a[j]=0;

             }

             a[i] = 0;

         }

     }  

     public static void main(String[] args)

     {

         int[] a = new int[9];

         a[0] = 1;  

         for(int b=1; b<a.length; b++){

             a[b] = 1;

             for(int c=b+1; c<a.length; c++){

                 a[c] = 1;

                 String s = "A" + (char)(b+'A') + (char)(c+'A');

                 f(s,a);

                 a[c] = 0;

             }

             a[b] = 0;

         }

     }

 }

 public class _4分小组 {

      public static int count=0;

       public static void main(String[] args) {

             char[] s ={'A','B','C','D'};

             paixiu(s, 0, s.length-1);

             System.out.println(count);

       }

 //  交换前缀

   public static void swap(char[] s,int i,int j){

       char temp = s[i];

       s[i] = s[j];

       s[j] = temp;

   }

 //  进行排列

   public static void paixiu(char[] s,int from,int to){

       if (to <= 1) {

             return;

       }if (from == to) {

         System.out.println(s);

         count++;

       }else{

           for (int i = from; i <= to; i++) {

             swap(s, i, from);//当前字符，与头一个交换

             paixiu(s, from+1, to);//除了第一个，剩下的进行排序

             swap(s, from, i);//把交换的换回来位置

         }

       }

   }

 }