http://acm.hdu.edu.cn/showproblem.php?pid=1013
#include<stdio.h>
int main()
{
    char tp[1001];       
    while(scanf("%s",tp)!=EOF)
    {
        int sum=0;
        char *p=tp;
        if(strcmp(tp,"0")==0)       
            break;
        /*
        下面的变量要定义到上面去，否则会出现语法错误，如下 
          int sum = 0;
        char *p = tp;
     *************************************    
        0_0_1232530_20045.c
        0_0_1232530_20045.c(9) : error C2143: 语法错误 : 缺少“;”(在“类型”的前面)
        0_0_1232530_20045.c(10) : error C2143: 语法错误 : 缺少“;”(在“类型”的前面)
        0_0_1232530_20045.c(11) : error C2065: “p” : 未声明的标识符
        0_0_1232530_20045.c(11) : error C2100: 非法的间接寻址
        0_0_1232530_20045.c(13) : error C2065: “sum” : 未声明的标识符
        0_0_1232530_20045.c(13) : error C2100: 非法的间接寻址
     **************************************        
        */
        while(*p!='\0')
        {
            sum += *p - '0';
            while(sum/10)
                sum = sum%10 + sum/10;
            p++;
        }
        printf("%d\n",sum);
    }
    return 0;
}