设计一个程序,输入某天是几月几日,要求算出这一天是本年的第几天?答:include <iostream> using namespace std;int main(){ int y,m,d,d1,i,mon[13]= {0,31,28,31,30,31,30,31,31,30,31,30,31};scanf("%d%d%d",&y,&m,&d);mon[2]+=(y%4==0&&y%100||y%400==0);if(y<1||m<1||m>12||d<1||d>mon[m]){ printf("Date input ...