程序分析：以3月5日为例，应该先把前两个月的加起来，然后再加上5天即本年的第几天，特殊情况，闰年且输入月份大于3时需考虑多加一天。

one

#include <stdio.h>main()

{

int year,month,day,days; int month1,month2,month3,month4,month5,month6,month7,month8,month9,month10,month11; month1=31;month2=month1+28,month3=month2+31;month4=month3+30;month5=month4+31;month6=month5+30; month7=month6+31;month8=month7+31;month9=month8=30;month10=month9+31,month11=month10+30; printf("Please enter your birthday:"); scanf("%d.%d.%D",&year,&month,&day); switch(month) { case 1 : days = day; break; case 2 : days = month1 + day; break; case 3 : days = month2 + day; break; case 4 : days = month3 + day; break; case 5 : days = month4 + day; break; case 6 : days = month5 + day; break; case 7 : days = month6 + day; break; case 8 : days = month7 + day; break; case 9 : days = month8 + day; break; case 10 : days = month9 + day; break; case 11 : days = month10 + day; break; case 12 : days = month11 + day; break; default :printf("I can't solve it"); break;

}

if((year%4==0&&year%100!=0)||year%400==0)

{

if(month>=3)

days++;

}

printf("your birthday is %d",days of the year”,days);

return 0;

}

two:

#include <stdio.h>

main()

{

int day,month,year,sum,leap;

printf("\nplease input year,month,day\n");

scanf("%d,%d,%d",&year,&month,&day);

switch(month)/*先计算某月以前月份的总天数*/

{　case 1:sum=0;break;　case 2:sum=31;break;　case 3:sum=59;break;　case 4:sum=90;break;　case 5:sum=120;break;　case 6:sum=151;break;　case 7:sum=181;break;　case 8:sum=212;break;　case 9:sum=243;break;　case 10:sum=273;break;　case 11:sum=304;break;　case 12:sum=334;break;　default:printf("data error");break;}

sum=sum+day; 　/*再加上某天的天数*/　if(year%400==0||(year%4==0&&year%100!=0))/*判断是不是闰年*/　　

leap=1;　

else　　

leap=0;

if(leap==1&&month>2)/*如果是闰年且月份大于2,总天数应该加一天*/sum++;

printf("It is the %dth day.",sum);

return 0;

}