c语言题目,求18题答案,多谢大佬!答:include <stdio.h>int days(int y, int m, int d);int main(){int year,month,day,answer;printf("请输入一个日期yyyy-mm-dd\n");scanf("%d-%d-%d",&year,&month,&day);answer = days(year,month,day);if (answer>0) {printf("%d-%d-%d 是该年的第 %d 天.\n", year, ...