【数根】2022-1-24

缘由程序设计 -- 数根（2）-编程语言-CSDN问答

void 数根()
{//缘由https://ask.csdn.net/questions/7635593?spm=1005.2025.3001.5141
	std::string n;
	int m = 0, a = 0;
	std::cin >> n;
	while (n[a] != '\0')m += n[a++] - '0';
	a = 0;
	while (m)a += m - m / 10 * 10, m /= 10,
		(m == 0 && a > 9 ? m = a, a = 0 : 0);
	std::cout << a << std::endl;
}