输入数据有多组，每组占一行，数据格式为YYYY/MM/DD组成
main()
{

int year,month,day;
while(scanf("%d",&year)&&scanf("%d",&day)&&scanf("%d",&month)!=EOF)
{
int sum=0;
switch(month)
{
case 1: sum=day;break;
case 2: sum=31+day;break;
case 3: sum=59+day;break;
case 4: sum=90+day;break;
case 5: sum=120+day;break;
case 6: sum=151+day;break;
case 7: sum=181+day;break;
case 8: sum=212+day;break;
case 9: sum=243+day;break;
case 10: sum=273+day;break;
case 11: sum=304+day;break;

case 12: sum=334+day;break;
default: printf("error.");
}
printf("sum");
printf("/n");
}
}

#include<iostream>
using namespace std;
int main()
{
 
int year,month,day;
while(scanf("%d",&year)&&scanf("%d",&day)&&scanf("%d",&month)!=EOF)
{
int sum=0;
switch(month)
{
case 1: sum=day;break;
case 2: sum=31+day;break;
case 3: sum=59+day;break;
case 4: sum=90+day;break;
case 5: sum=120+day;break;
case 6: sum=151+day;break;
case 7: sum=181+day;break;
case 8: sum=212+day;break;
case 9: sum=243+day;break;
case 10: sum=273+day;break;
case 11: sum=304+day;break;
 
case 12: sum=334+day;break;
default: printf("error.");
}
printf("%d\n",sum); //输出整数的格式
}
}

头文件，输出格式，一般还要加个润年吧，其它不懂了

想起来刚想说什么了，输入年月日还是按习惯吧，变成年日月还真无语要是不特别要求。