1 files changed, 64 insertions, 0 deletions
diff --git a/challenge-097/ulrich-rieke/cpp/ch-2.cpp b/challenge-097/ulrich-rieke/cpp/ch-2.cpp
new file mode 100644
index 0000000000..7fa22ce546
--- /dev/null
+++ b/challenge-097/ulrich-rieke/cpp/ch-2.cpp
@@ -0,0 +1,64 @@
+#include <iostream>
+#include <string>
+#include <vector>
+#include <map>
+#include <cstdlib>
+#include <algorithm>
+#include <numeric>
+
+bool isInputValid( const std::string & input , int n ) {
+  return input.length( ) % n == 0 ;
+}
+
+//how many digits must be changed to make them all equal
+int countToMakeAllEqual( const std::string & input ) {
+  std::map<std::string , int> frequencies ;
+  frequencies["0"] = 0 ;
+  frequencies["1"] = 0 ;
+  int len = input.length( ) ;
+  for ( int i = 0 ; i < len ; i++ ) {
+      frequencies[ input.substr( i , 1 )]++ ;
+  }
+  if ( frequencies[ "0" ] == len || frequencies[ "1" ] == len )
+      return 0 ;
+  int bigger = std::max( frequencies["0"] , frequencies[ "1" ] ) ;
+  return len - bigger ;
+}
+
+int main( int argc, char * argv[ ] ) {
+  if ( argc != 3 ) {
+      std::cerr << "There should be 2 arguments, call <challenge097_2> <string> <number>!" ;
+      return 1 ;
+  }
+  std::string input( argv[ 1 ] ) ;
+  int blocks { std::atoi( argv[ 2 ] ) } ;
+  if ( ! isInputValid( input , blocks ) ) {
+      std::cerr << "the number of digits in the binary string should be a multiple of " ;
+      std::cerr << blocks << " !" << std::endl ;
+      return 2 ;
+  }
+  int len = input.length( ) ;
+  int chunknumber = len / blocks ;
+  int chunklength { len / chunknumber } ;
+  std::vector<std::string> words ;
+  //for all blocks to be equal we transpose the blocks, that is the first letters
+  //of every block form a word, the second letters and so on
+  //we then see how many digits have to be flipped to make all digits equal
+  std::string transposed ;
+  for ( int i = 0 ; i < chunklength ; i++ ) {
+      for ( int j = 0 ; j < chunknumber ; j++ ) {
+    transposed.append( input.substr( i + j * chunklength , 1 ) ) ;
+    if ( transposed.length( ) == chunknumber ) {
+        words.push_back( transposed ) ;
+        transposed.clear( ) ;
+    }
+      }
+  }
+  std::vector<int> alterations ;
+  for ( std::string & word : words ) {
+      alterations.push_back( countToMakeAllEqual( word ) ) ;
+  }
+  std::cout << std::accumulate( alterations.begin( ) , alterations.end( ) , 0 )
+      << std::endl ;
+  return 0 ;
+}