- Added more guest contribution by Ulrich Rieke.

1 files changed, 86 insertions, 0 deletions

diff --git a/challenge-190/ulrich-rieke/cpp/ch-2.cpp b/challenge-190/ulrich-rieke/cpp/ch-2.cpp
new file mode 100644
index 0000000000..16b1055105
--- /dev/null
+++ b/challenge-190/ulrich-rieke/cpp/ch-2.cpp
@@ -0,0 +1,86 @@
+#include <iostream>
+#include <algorithm>
+#include <vector>
+#include <string>
+
+//find all combinations of 1 and 2 that add up to the given length
+std::vector<std::vector<int>> findAllCombinations( int len ) {
+  std::vector<std::vector<int>> allCombinations ;
+  std::vector<int> currentCombi ;
+  std::vector<std::vector<int>> thePermus ;
+  for ( int twos = 0 ; twos < len / 2 + 1 ; twos++ ) {
+      int ones = len - twos * 2 ;
+      for ( int i = 0 ; i < ones ; i++ ) {
+    currentCombi.push_back( 1 ) ;
+      }
+      for ( int i = 0 ; i < twos ; i++ ) {
+    currentCombi.push_back( 2 ) ;
+      }
+      allCombinations.push_back( currentCombi ) ;
+      currentCombi.clear( ) ;
+  }
+  //permute the combinations that contain both 1 and 2
+  for ( auto combi : allCombinations ) {
+      if ( std::find( combi.begin( ) , combi.end( ) , 1 ) != combi.end( )
+        && ( std::find( combi.begin( ) , combi.end( ) , 2 ) !=
+          combi.end( ))) {
+    std::vector<int> aCombi { combi } ;
+    while (std::next_permutation( aCombi.begin( ) , aCombi.end( ) )) {
+        thePermus.push_back( aCombi ) ;
+    }
+      }
+  }
+  //push the permutations to the existing combinations
+  for ( auto combi : thePermus ) {
+      allCombinations.push_back( combi ) ;
+  }
+  return allCombinations ;
+}
+
+//take the given number string apart according to the combination of
+//1's an 2's
+std::vector<int> findNumbers( const std::string & st , const
+      std::vector<int> & nums ) {
+  std::vector<int> numbers ;
+  int pos = 0 ;
+  for ( int i : nums ) {
+      numbers.push_back( std::stoi( st.substr( pos , i ))) ;
+      pos += i ;
+  }
+  return numbers ;
+}
+
+//transform every number into a letter
+std::string createWord( const std::vector<int> & numbers ) {
+  std::string word ;
+  if ( std::any_of( numbers.begin( ) , numbers.end( ) , []( int i ) {
+        return i > 26 ; })) {
+      return "" ;
+  }
+  else {
+      for ( int n : numbers ) {
+    word += static_cast<char>( n + 64 ) ;
+      }
+      return word ;
+  }
+}
+
+int main( ) {
+  std::cout << "Please enter a string consisting only of digits!\n" ;
+  std::string line ;
+  std::cin >> line ;
+  std::vector<std::string> allWords ;
+  std::vector<std::vector<int>> allCombinations ( findAllCombinations(
+        line.length( ))) ;
+  for ( auto & comb : allCombinations ) {
+      std::string word ( createWord( findNumbers( line , comb ))) ;
+      if ( word.length( ) > 0 )
+    allWords.push_back( word ) ;
+  }
+  std::sort( allWords.begin( ) , allWords.end( ) ) ;
+  for ( const auto & w : allWords ) {
+      std::cout << w << ' ' ;
+  }
+  std::cout << std::endl ;
+  return 0 ;
+}