1 files changed, 39 insertions, 0 deletions
diff --git a/challenge-046/ulrich-rieke/cpp/ch-2.cpp b/challenge-046/ulrich-rieke/cpp/ch-2.cpp
new file mode 100644
index 0000000000..a363ff9209
--- /dev/null
+++ b/challenge-046/ulrich-rieke/cpp/ch-2.cpp
@@ -0,0 +1,39 @@
+#include <string>
+#include <vector>
+#include <utility>
+#include <iostream>
+
+std::string flip( const std::string & doorstate ) {
+  if ( doorstate == "open" ) {
+      return "closed" ;
+  }
+  else {
+      return "open" ;
+  }
+}
+
+int main( ) {
+  std::vector<std::pair<std::string, int> > theDoors ;
+      for ( int i = 1 ; i < 501 ; i++ ) {
+    theDoors.push_back( std::make_pair( "open" , i ) ) ;
+      }
+  for ( int i = 2 ; i < 501 ; i++ ) {
+      if ( i < 251 ) {
+    for ( int j = i ; j < 501 ; j += i ) {
+        const std::string state {theDoors[ j - 1].first } ;
+        std::string newState { flip ( state ) } ;
+        theDoors[ j - 1 ] = std::make_pair( newState , theDoors[ j - 1 ].second ) ;
+    }
+      }
+      else {
+    theDoors[ i - 1 ] = std::make_pair( flip( theDoors[ i - 1 ].first ) ,
+          theDoors[ i - 1 ].second ) ;
+      }
+  }
+  for ( auto & p : theDoors ) {
+      if ( p.first == "open" ) {
+    std::cout << "Door " << p.second << " is open!\n" ;
+      }
+  }
+  return 0 ;
+}