Jc.java (JieCheng)

//BigInteger 不能直接计算出10000的阶乘，下面这个程序仅需1524ms
//100000的阶乘耗时163091 ms
class Jc{
  private int digit;
  private int[] data;
  public Jc(){
   digit = 1;
   data = new int[4000000];
   data[0] = data[1] = 1;
  }
  public static void main(String[] args){
   long start = System.currentTimeMillis();
   Jc jc2 = new Jc();
   jc2.run(10000);
   long end = System.currentTimeMillis();
   System.out.println("Spent "+(end-start)+" ms.");
  }
  public void run(int n){
   for(int i=1;i<=n;i++){
       for(int j=1;j<=digit;j++){
           data[j] *= i;
       }
       for(int k=1;k<=digit;k++){
           if(data[k]>=10){
               for(int r=1;r<=digit;r++){
                   if(data[digit]>=10){
                       digit++;
                   }
                   data[r+1]+=data[r]/10;
                   data[r]=data[r]%10;
               }
           }
       }
   }
   for(int k=digit;k>0;k--){
       System.out.print(data[k]);
   }
System.out.println();
System.out.println(digit);
  }
}