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  1.     #include <stdio.h>
  2.  
  3.     unsigned long AddDays(unsigned long StartDay, unsigned long Days)
  4.     {
  5.       unsigned long year = StartDay / 10000, month = StartDay / 100 % 100 - 1, day = StartDay % 100 - 1;
  6.  
  7.       while (Days)
  8.       {
  9.         unsigned daysInMonth[2][12] =
  10.         {
  11.           { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }, // 365 days, non-leap
  12.           { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }  // 366 days, leap
  13.         };
  14.  
  15.         int leap = !(year % 4) && (year % 100 || !(year % 400));
  16.  
  17.         unsigned daysLeftInMonth = daysInMonth[leap][month] - day;
  18.  
  19.         if (Days >= daysLeftInMonth)
  20.         {
  21.           day = 0;
  22.           Days -= daysLeftInMonth;
  23.           if (++month >= 12)
  24.           {
  25.             month = 0;
  26.             year++;
  27.           }
  28.         }
  29.         else
  30.         {
  31.           day += Days;
  32.           Days = 0;
  33.         }
  34.       }
  35.  
  36.       return year * 10000 + (month + 1) * 100 + day + 1;
  37.     }
  38.  
  39.     int main(void)
  40.     {
  41.       unsigned long testData[][2] =
  42.       {
  43.         { 20130228, 0 },
  44.         { 20130228, 1 },
  45.         { 20130228, 30 },
  46.         { 20130228, 31 },
  47.         { 20130228, 32 },
  48.         { 20130228, 365 },
  49.         { 20130228, 366 },
  50.         { 20130228, 367 },
  51.         { 20130228, 365*3 },
  52.         { 20130228, 365*3+1 },
  53.         { 20130228, 365*3+2 },
  54.       };
  55.  
  56.       unsigned i;
  57.  
  58.       for (i = 0; i < sizeof(testData) / sizeof(testData[0]); i++)
  59.         printf("%lu + %lu = %lu\n", testData[i][0], testData[i][1], AddDays(testData[i][0], testData[i][1]));
  60.  
  61.       return 0;
  62.     }
  63.  
  64.  
Success #stdin #stdout 0s 1832KB
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stdin
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Standard input is empty
stdout
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20130228 + 0 = 20130228
20130228 + 1 = 20130301
20130228 + 30 = 20130330
20130228 + 31 = 20130331
20130228 + 32 = 20130401
20130228 + 365 = 20140228
20130228 + 366 = 20140301
20130228 + 367 = 20140302
20130228 + 1095 = 20160228
20130228 + 1096 = 20160229
20130228 + 1097 = 20160301
https://ideone.com/9F88ow
language:
C99 (gcc 8.3)
created:
11 years ago
visibility:
public

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