- Added guest contribution by Ulrich Rieke.

1 files changed, 44 insertions, 0 deletions

diff --git a/challenge-138/ulrich-rieke/cpp/ch-1.cpp b/challenge-138/ulrich-rieke/cpp/ch-1.cpp
new file mode 100644
index 0000000000..09201bac1b
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+++ b/challenge-138/ulrich-rieke/cpp/ch-1.cpp
@@ -0,0 +1,44 @@
+#include <iostream>
+#include <cstdlib>
+#include <chrono>
+#include <array>
+#include <algorithm>
+
+//the number of weekdays in a year depends on the weekday of New Year. Every year
+//has 52 full weeks, with 52 * 5 weekdays. In a non-leap year, the 31 Dec has the
+//same weekday as New Year. If this is a weekday it adds a 261st weekday. In leap
+//years, 30 Dec has the same weekday, so that we may have to add 0 , 1 or even
+//2 weekdays to the minimum number of 52 * 5 = 260 weekdays, depending on the
+//weekday of New Year
+
+int main( int argc , char * argv[ ] ) {
+  int year = std::atoi( argv[ 1 ] ) ;
+  int weekdays = 0 ;
+  auto newYear = std::chrono::year( year ) / std::chrono::month( 1 ) /
+      std::chrono::day( 1 ) ;
+  auto startWeekday = std::chrono::year_month_weekday( newYear ) ;
+  auto newYearWeekday = startWeekday.weekday( ) ;
+  if ( ! (newYear.year().is_leap( )) ) {
+      if ( newYearWeekday == std::chrono::Saturday || newYearWeekday ==
+        std::chrono::Sunday )
+    weekdays = 52 * 5 ;
+      else
+    weekdays = 52 * 5 + 1 ;
+  }
+  else {
+      std::array<std::chrono::weekday , 4> startDays { std::chrono::Monday ,
+        std::chrono::Tuesday , std::chrono::Wednesday ,
+              std::chrono::Thursday } ;
+      if ( newYearWeekday == std::chrono::Saturday ) {
+    weekdays = 52 * 5 ;
+      }
+      if ( newYearWeekday == std::chrono::Friday || newYearWeekday ==
+        std::chrono::Sunday )
+    weekdays = 52 * 5 + 1 ;
+      if ( std::any_of( startDays.begin( ) , startDays.end( ) ,
+          [newYearWeekday]( auto d ) { return d == newYearWeekday ;} ))
+    weekdays = 52 * 5 + 2 ;
+  }
+  std::cout << weekdays << std::endl ;
+  return 0 ;
+}