略坑的一道题。
#include <stdio.h> char str[1000]; int f(int n){ int s = 0; while(n){ s += n % 10; n /= 10; } return s; } int main(){ int n, s; while(scanf("%s", str), str[0] - '0'){ s = 0; for(int i = 0; str[i] != '\0'; ++i) s += str[i] - '0'; while(s > 9) s = f(s); printf("%d\n", s); } return 0; }