Digital Roots

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 79339    Accepted Submission(s): 24800

Problem Description

The
digital root of a positive integer is found by summing the digits of
the integer. If the resulting value is a single digit then that digit is
the digital root. If the resulting value contains two or more digits,
those digits are summed and the process is repeated. This is continued
as long as necessary to obtain a single digit.

For example,
consider the positive integer 24. Adding the 2 and the 4 yields a value
of 6. Since 6 is a single digit, 6 is the digital root of 24. Now
consider the positive integer 39. Adding the 3 and the 9 yields 12.
Since 12 is not a single digit, the process must be repeated. Adding the
1 and the 2 yeilds 3, a single digit and also the digital root of 39.

Input

The
input file will contain a list of positive integers, one per line. The
end of the input will be indicated by an integer value of zero.

Output

For each integer in the input, output its digital root on a separate line of the output.

Sample Input

24

39

0

Sample Output

6

3

Source

Greater New York 2000

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1013

分析：很智障的题，我当时一直在想这怎么处理数字问题，没考虑这输入数字无限大的问题，sb啊，直接字符串从低到高位搞一下就好了，每一位处理即可！
下面给出AC代码：

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 int main()
 4 {
 5     string str;
 6     while(cin>>str&&str!="0")
 7     {
 8         int num=0;
 9         for(int i=0;i<str.length();i++)
10         {
11             num+=str[i]-‘0‘;
12             if(num>9)
13                 num=num/10+num%10;
14         }
15         cout<<num<<endl;
16     }
17     return 0;
18 }