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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. int days_in_month (int y, int m) {
  5.   // Fourth, eleventh, ninth, and sixth,
  6.   // thirty days to each we fix. 
  7.   if ((m==4)||(m==11)||(m==9)||(m==6)) return 30; 
  8.   // Every other, thirty-one,
  9.   // except the second month alone,
  10.   if (m!=2) return 31;
  11.   // which hath twenty-eight, in fine,
  12.   // till leap-year give it twenty-nine.
  13.   if ((y%400)==0) return 29; // leap year
  14.   if ((y%100)==0) return 28; // not a leap year
  15.   if ((y%4)==0)   return 29; // leap year
  16.   return 28; // not a leap year 
  17. }
  18.  
  19. int ymdToWeekNumber (int y, int m, int d) {
  20.   // reject out-of-range dates
  21.   if ((y < 1901)||(y > 2099)) return 0;
  22.   if ((m < 1)||(m > 12)) return 0;
  23.   if ((d < 1)||(d > 31)) return 0;
  24.   // (It is useful to know that Jan. 1, 1901 was a Tuesday)
  25.   // compute adjustment for dates within the year
  26.   //     If Jan. 1 falls on: Mo Tu We Th Fr Sa Su
  27.   // then the adjustment is:  6  7  8  9  3  4  5
  28.   int adj = (((y-1901) + ((y-1901)/4) + 4) % 7) + 3;
  29.   // compute day of the year (in range 1-366)
  30.   int doy = d;
  31.   if (m > 1) doy += 31;
  32.   if (m > 2) {
  33.     if ((y%4)==0) doy += 29;
  34.     else doy += 28;
  35.   }
  36.   if (m > 3) doy += 31;
  37.   if (m > 4) doy += 30;
  38.   if (m > 5) doy += 31;
  39.   if (m > 6) doy += 30;
  40.   if (m > 7) doy += 31;
  41.   if (m > 8) doy += 31;
  42.   if (m > 9) doy += 30;
  43.   if (m > 10) doy += 31;
  44.   if (m > 11) doy += 30;
  45.   // compute week number
  46.   int wknum = (adj + doy) / 7;
  47.   // check for boundary conditions
  48.   if (wknum < 1) {
  49.     // last week of the previous year
  50.     // check to see whether that year had 52 or 53 weeks
  51.     // re-compute adjustment, this time for previous year
  52.     adj = (((y-1902) + ((y-1902)/4) + 4) % 7) + 3;
  53.     // all years beginning on Thursday have 53 weeks
  54.     if (adj==9) return 53;
  55.     // leap years beginning on Wednesday have 53 weeks
  56.     if ((adj==8) && ((y%4)==1)) return 53;
  57.     // other years have 52 weeks
  58.     return 52;
  59.   }
  60.   if (wknum > 52) {
  61.     // check to see whether week 53 exists in this year
  62.     // all years beginning on Thursday have 53 weeks
  63.     if (adj==9) return 53;
  64.     // leap years beginning on Wednesday have 53 weeks
  65.     if ((adj==8) && ((y%4)==0)) return 53;
  66.     // other years have 52 weeks
  67.     return 1;
  68.   }
  69.   return wknum;
  70. }
  71.  
  72. int main() {
  73. 	int errcnt = 0;
  74. 	int yyyy=1901, mo=1, dd=1, wd=2, wn=1;
  75. 	cout << "Simple week number test\n";
  76. 	while (yyyy<2100) {
  77. 		int wntest = ymdToWeekNumber(yyyy,mo,dd);
  78. 		if (wn != wntest) {
  79. 			errcnt++;
  80. 			if (errcnt <= 50) {
  81. 				cout << yyyy << "/" << mo << "/" << dd << "  " << wn << "  " << wntest << "\n";
  82. 			}
  83. 		}
  84. 		dd++;
  85. 		if (dd > days_in_month(yyyy,mo)) {
  86. 			dd = 1;
  87. 			mo++;
  88. 			if (mo > 12) {
  89. 				mo = 1;
  90. 				yyyy++;
  91. 			}
  92. 		}
  93. 		wd++;
  94. 		if (wd > 7) {
  95. 			wd = 1;
  96. 			wn++;
  97. 			if (((mo==12) && (dd>=29)) || ((mo==1) && (dd<=4))) wn = 1;
  98. 		}
  99. 	}
  100. 	cout << "Error count: " << errcnt << "\n";
  101. 	return 0;
  102. }
Success #stdin #stdout 0.01s 5516KB
comments (?)
stdin 
Standard input is empty
stdout 
Simple week number test
Error count: 0
https://ideone.com/G4tE7P
language:
C++ (gcc 8.3)
created:
3 years ago
visibility:
secret

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