输入一个日期(年、月、日),计算从当年1月1日起到这一天的天数答:include <stdio.h> int day_of_year(int a[13],int b[13],int year,int month,int day);int main(void){ int a[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};int b[13]={0,31,29,31,30,31,30,31,31,30,31,30,31};int yy,mm,dd,sum;printf("输入年:");scanf...