day of the year

day_of_the_year.c

#include <stdio.h>

int leap(int year)
{
    return (0 == year % 4 && 0 != year % 100) || (0 == year % 400);
}

int day_number(int d, int m, int y)
{
    int days_in_mo[12] = {31, 28 + leap(y), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    int day_num        = 0;

    for ( int i = 0; i < (m-1); i++ )
        day_num += days_in_mo[i];

    day_num += d;

    return day_num;
}


int main( int argc, char *argv[] )
{
    int day, month, year;

    sscanf( argv[1], "%d", &day );
    sscanf( argv[2], "%d", &month );
    sscanf( argv[3], "%d", &year );

    printf( "Day number is: %d\n", day_number(day, month, year) );

    return 0;
}