HDU 1013 (13.10.29)

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

题意: 就是把某个数的各位数字全部加起来, 然后判断是否是各位数, 若不是的话, 继续重复第一句话说的, 把得到的数字的各位数全部加起来, 如此往复, 直到得到个位数~

坑点: 输入的数字可能很大, 所以要小心

AC代码:

#include<stdio.h>

int main() {
    char str[2222];
    while(scanf("%s", str), str[0] != '0') {
        int sum = 0;
        int n = 0;
        int i = 0;
        while(str[i]) {
            n = n + str[i++] - '0';
        }
        while(n > 0) {
            sum += n % 10;
            n = n / 10;
            if(n == 0 && sum > 9) {
                n = sum;
                sum = 0;
            }
        }
        printf("%d\n", sum);
    }
    return 0;
}