ACM 数论 hdu 1013 Digital Roots

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

24390

 

Sample Output

63

 


题意：输入一个数字，对其每个位数相加，如果小于10，输出。否则再将每个位数相加，直到小于10.

注意点： ①数字可能非常的大，所以要用字符串，不要用int之类的
                ②没必要将全算完再算各位数相加，可以只要超出就缩小数值



答案：

#include<stdio.h>
#include<string.h>
 
 
int main()  
{  
    char ch[1010];  
    int s;  
    while (~scanf("%s",ch))  
    {  
        if (ch[0]=='0')  
            break;  
        s=0;  
        int len=strlen(ch);  
        for (int i=0; i<len; i++)  
        {  
            s+=ch[i]-'0';  
            if (s>=9)  
            {  
                s=s%10+s/10;  
               
            }  
        }  
        printf ("%d\n",s);  
    }  
    return 0;  
}