Persistent Numbers(大数+发现java注意点!!!）

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Problem：

Persistent Numbers

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 3029		Accepted: 1470

Description

The multiplicative persistence of a number is defined by Neil Sloane (Neil J.A. Sloane in The Persistence of a Number published in Journal of Recreational Mathematics 6, 1973, pp. 97-98., 1973) as the number of steps to reach a one-digit number when repeatedly multiplying the digits. Example: 

679 -> 378 -> 168 -> 48 -> 32 -> 6.

That is, the persistence of 679 is 6. The persistence of a single digit number is 0. At the time of this writing it is known that there are numbers with the persistence of 11. It is not known whether there are numbers with the persistence of 12 but it is known that if they exists then the smallest of them would have more than 3000 digits. 
The problem that you are to solve here is: what is the smallest number such that the first step of computing its persistence results in the given number?

Input

For each test case there is a single line of input containing a decimal number with up to 1000 digits. A line containing -1 follows the last test case.

Output

For each test case you are to output one line containing one integer number satisfying the condition stated above or a statement saying that there is no such number in the format shown below.

Sample Input

0
1
4
7
18
49
51
768
-1

Sample Output

10
11
14
17
29
77
There is no such number.
2688

Source

Waterloo local 2003.07.05

错误代码：

import java.util.*;

import java.io.*;
import java.math.*;
import java.text.*;


public class Main{
public static void main(String[] args)
{
BigInteger x;
int i;
        String s;
Scanner cin=new Scanner(System.in);
while(cin.hasNext())
{
x=cin.nextBigInteger();
if(x.compareTo(BigInteger.valueOf(-1))==0)
break;
if(x.compareTo(BigInteger.valueOf(10))<0)
{
System.out.println("1"+x);
}
else
{
                                s="";
for(i=9;i>=2;i--)
{
while(x.mod(BigInteger.valueOf(i))==BigInteger.valueOf(0))//这样写poj是wa！！！
{
                                                s=i+s;
x=x.divide(BigInteger.valueOf(i));
}
}
if(x.compareTo(BigInteger.ONE)!=0)
{
System.out.println("There is no such number.");
}
else
{
System.out.println(s);
}
}
}
}

}

发现后改正AC代码：

import java.util.*;
import java.io.*;
import java.math.*;
import java.text.*;


public class Main{
public static void main(String[] args)
{
BigInteger x;
int i;
        String s;
Scanner cin=new Scanner(System.in);
while(cin.hasNext())
{
x=cin.nextBigInteger();
if(x.compareTo(BigInteger.valueOf(-1))==0)
break;
if(x.compareTo(BigInteger.valueOf(10))<0)
{
System.out.println("1"+x);
}
else
{
                                s="";
for(i=9;i>=2;i--)
{
while(x.mod(BigInteger.valueOf(i)).compareTo(BigInteger.valueOf(0))==0)//就改了这一句就AC了！！！
{
                                                s=i+s;
x=x.divide(BigInteger.valueOf(i));
}
}
if(x.compareTo(BigInteger.ONE)!=0)
{
System.out.println("There is no such number.");
}
else
{
System.out.println(s);
}
}
}
}
}