How i make restrictions into a variable - c

Question

I'm new in C language and I have a question.
I have to create a program where I put the number of days I worked in every single month.
I already done that but I need to restrict the days by the number of days of each month .
Example : January more than 1 day less than 31 , February more than 1 but less than 28 etc...
int numero_dias, mes;
for (mes = 0; mes != 12; mes++){
do {
printf("Digite o
numero de dias trabalhados no mes %s: ", meses[mes]);
scanf("%d", &numero_dias);
if (meses[mes] == 0 meses[mes] == 2 meses[mes] == 4 meses[mes] == 6 meses[mes] == 7 meses[mes] == 9 meses[mes] == 11 ){
if (numero_dias < -1 || numero_dias > 31){
continue;
}else{
break;
}
}

Answer 1

If I understand your question correctly, you want to:
Enter the number of days you worked in a month;
Check that the number of days you entered does not exceed the number of days for that month.
So, if you're entering the number of days you worked for the month of January, that number has to be between 0 and 31 (I'm assuming it's possible you can work zero days in a month). For the month of February it has to be between 0 and 28 (29 in a leap year), for April it has to be between 0 and 30, etc.
An easy way to do this is to set up an array to keep track of the number of days per month, indexed by the month number (0 for January, 1 for February, etc.):
/**
* We're declaring this const so that we can't accidentally change any
* of the entries in the array.
*/
const int days[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
We'll have to add some special-case processing for February to deal with leap years, but for this first pass we won't worry about it.
It may also be useful to have another array1 for the month names, since you try to display that in your loop:
const char *names[] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
So now your loop becomes:
for (mes = 0; mes < 12; mes++ )
{
do
{
printf( "Digite o numero de dias trabalhados no mes %s: ", names[mes] );
scanf ( "%d", &numero_dias );
} while ( numero_dias < 0 || numero_dias > days[mes] );
// do something with numero_dias
}
The inner do loop will repeat while numero_dias is outside the range of 0 and days[mes]. So when mes is 0, days[mes] is 31, when mes is 3, days[mes] is 30, etc.
February (1) is a special case - it can be either 28 or 29 days. So we need to modify the condition of the do loop slightly:
do
{
...
} while ( numero_dias < 0 || numero_dias > ( mes != 1 ? days[mes] : feb_days() ) );
The expression mes != 1 ? days[mes] : feb_days() checks to see if mes corresponds to February (1) - if it doesn't, then we use the value in days[mes] (January, March, April, May, etc.). If it does, then we call another function feb_days() that returns the number of days in February for the current year.
So the condition in the do-while loop now checks to see if numero_dias is less than zero or greater than the number of days for the current month, with a special case for February.
To get the number of days in February for the current year, you can do the following:
int feb_days( void )
{
time_t now = time( NULL ); // Get number of seconds since 1970-01-01
struct tm *utc = gmtime( &now ); // Break time into year, month, day, etc.
int days = 28; // default number of days in Feb
return days + (utc->tm_year % 4 == 0 && (utc->tm_year % 100 != 0 || utc->tm_year % 400 == 0 ));
}
The expression (utc->tm_year % 4 == 0 && (utc->tm_year % 100 != 0 || utc->tm_year % 400 == 0 )) will evaluate to 1 if the current year is divisible by 4 and it's not divisible by 100 or it is divisible by 400. If any of those conditions are not true, then it evaluates to 0. So if this is not a leap year, we return 28 + 0 == 28 days. If it is a leap year, we return 28 + 1 == 29 days.
There's a lot more bulletproofing that needs to be done - you need to check the return value of scanf to make sure your input was actually read correctly (and take action to clear the input stream if it wasn't), you probably want to give your user a way to cancel the input operation, etc., but this should get you started.
Actually, we'd use a single array of a struct type instead of separate arrays, but I'm trying to keep things basic.