这个代码是根据输入的年月日来判断是一年的第几天，但老是出错，在此虚心求教!

你写的有点麻烦

初学者一枚，请多关照

用if最好加作用域｝大括号

你把代码发给我，我给你改

#include<stdio.h>
int main()
{
int year, month, day, sum, flag = 1;
printf("Please input year,month and day:");
scanf("%d%d%d", &year, &month, &day);
if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0))
flag == 1;
else
flag == 0;
switch (month - 1) {
case 12:sum += 31;
case 11:sum += 30;
case 10:sum += 31;
case 9:sum += 30;
case 8:sum += 31;
case 7:sum += 31;
case 6:sum += 30;
case 5:sum += 31;
case 4:sum += 30;
case 3:sum += 31;
case 2:sum += 30;
case 1:sum += 31;
default:printf("error");
}
sum += day;
printf("It's the %dth day of the year",sum);
return 0;
}

我的也是这样啊

#include<stdio.h>
int main()
{
int year, month, day, sum, flag = 0;
printf("Please input year,month and day:");
scanf("%d%d%d", &year, &month, &day);
if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0))
{
flag = 1;
}
if (flag == 1)
{
switch (month - 1)
{
case 11:
sum += 30;
case 10:
sum += 31;
case 9:
sum += 30;
case 8:
sum += 31;
case 7:
sum += 31;
case 6:
sum += 30;
case 5:
sum += 31;
case 4:
sum += 30;
case 3:
sum += 31;
case 2:
sum += 29;
case 1:
sum += 31;
default:
printf("error");
}
}
else
{
switch (month - 1)
{
case 11:
sum += 30;
case 10:
sum += 31;
case 9:
sum += 30;
case 8:
sum += 31;
case 7:
sum += 31;
case 6:
sum += 30;
case 5:
sum += 31;
case 4:
sum += 30;
case 3:
sum += 31;
case 2:
sum += 28;
case 1:
sum += 31;
default:
printf("error");
}
}
sum += day;
printf("It's the %d th day of the year", sum);
return 0;
}

应该没问题

得到的还是同样的结果

把scanf拆成3句试试，连续%d是没空格的

#include<stdio.h>
int main()
{
int year, month, day, sum, flag = 1;
printf("Please input year,month and day:");
scanf("%d %d %d", &year, &month, &day);
if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0))
flag == 1;
else
flag == 0;
sum= day;
switch (month - 1) {
case 11:sum += 30;
case 10:sum += 31;
case 9:sum += 30;
case 8:sum += 31;
case 7:sum += 31;
case 6:sum += 30;
case 5:sum += 31;
case 4:sum += 30;
case 3:sum += 31;
case 2:sum += 28+flag;
case 1:sum += 31;
}
printf("It's the %dth day of the year",sum);
return 0;
}

#include<stdio.h>
int main()
{
int year, month, day, sum, flag = 0;
printf("Please input year,month and day:\n");
scanf("%d%d%d", &year, &month, &day);
if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0))
flag = 1;
switch (month - 1)
{
case 11: sum += 30;
case 10: sum += 31;
case 9: sum += 30;
case 8: sum += 31;
case 7: sum += 31;
case 6: sum += 30;
case 5: sum += 31;
case 4: sum += 30;
case 3: sum += 31;
case 2: sum += 28;
case 1: sum += 31; break;
default: printf("error");
}
sum += day + flag;
printf("It's the %dth day of the year", sum);
return 0;
}

#include<stdio.h>
int main() {
int year, month, day, sum=0, flag = 0;
printf("Please input year,month and day:");
scanf("%d%d%d", &year, &month, &day);
if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0))
flag =1;
while(month) {
switch (month-1) {
case 10:
case 8:
case 7:
case 5:
case 3:
case 1:
sum += 31;
break;
case 11:
case 9:
case 6:
case 4:
sum += 30;
break;
case 2:
sum += 28+flag;
break;
case 0:
break;
default:
printf("error\n");
return 0;
}
month--;
}
sum += day;
printf("It's the %dth day of the year\n",sum);
return 0;
}
注意switch-case要配合break使用。