ex_5-8.c

   1 #include <stdio.h>
   2
   3 static char daytab[2][13] =
   4 {
   5         { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
   6         { 0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
   7 };
   8
   9 /* set day of year based on month and day */
  10 int day_of_year(int year, int month, int day)
  11 {
  12         int i, leap;
  13
  14         if(year < 1752 || month > 12 || month < 1 || day < 1) { return -1; }
  15
  16         leap = year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
  17         if(day > daytab[leap][month]) { return -1; } // day month pair OK?
  18
  19         for( i = 1; i < month; i++)
  20                 day += daytab[leap][i];
  21         return day;
  22 }
  23
  24 /* get month, day from day of year */
  25 int month_day(int year, int yearday, int *pmonth, int *pday)
  26 {
  27         int i, leap;
  28
  29         if(year < 1752) { return -1; }
  30
  31         leap = year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
  32         if((leap && yearday > 366) || (!leap && yearday > 365)) { return -1; }
  33
  34         for(i = 1; yearday > daytab[leap][i]; i++)
  35                 yearday -= daytab[leap][i];
  36         *pmonth = i;
  37         *pday = yearday;
  38         return 1;
  39 }
  40
  41 int main()
  42 {
  43         int ans, month, day;
  44         ans = day_of_year(2009, 2, 1);
  45         printf("%d\n", ans);
  46         ans = month_day(2009, 34, &month, &day);
  47
  48         if(ans)
  49                 printf("Day: %d\tMonth:%d\n", day, month);
  50
  51         int yearday, year = 2009;
  52         int leap = year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
  53
  54         for(month = 1; month <= 12; ++month)
  55         {
  56                 printf("\n");
  57                 day = 0;
  58                 while(++day <= daytab[leap][month])
  59                 {
  60                         yearday = day_of_year(year, month, day);
  61                         printf("Y: %d\tM: %d\tD: %d\t->\tYD:%d\n", year, month, day, yearday);
  62                 }
  63                 printf("\n");
  64         }
  65         return 1;
  66 }