HDU 1006 Digital Roots-优快云博客

本文介绍了一个简单的算法，用于计算任意正整数的数字根。数字根是指通过不断累加整数的所有位直到结果为一位数的过程。文章提供了一段C++代码实现，演示了如何高效地计算数字根。

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

题目简单~：

#include <iostream>
using namespace std;

int main(int argc, char *argv[])
{
	char c;
	int sum = 0;
	
	while(c = getchar())
	{
		if(c == '\n')
		{
			cout << sum << endl;
		 
		 	c = getchar();
		 	if(c == '0')
		 		break;
	 		else
	 			sum = c - '0';
	 			
 			continue;
		}	
		
		sum += c - '0';
		
		if(sum > 9)
		{
			sum = sum%10 + sum/10;
		}
			
	} 
	
	return 0;
}