#include #include #include #include #include #include using namespace std; using namespace std::chrono; using clock_type = steady_clock; template < size_t N > auto measure( function< void( string& ) > _func ) -> double { auto _s{ clock_type::now() }; for ( size_t _i{ 0 }; _i < N; ++_i ) { string _s{ "Short string." }; string _l{ "A string too long to apply for short string optimization" }; _func( _s ); _func( _l ); _s.push_back( '?' ); _l.push_back( '?' ); } auto _e{ clock_type::now() }; return duration< double >{ _e - _s }.count(); } auto reversedata_1( string& str ) -> void { stack< char > s; int i = 0; for ( char c = str[0]; c != '\0'; ) { s.push( c ); c = str[ ++i ]; } char arr[ i + 1 ]; int j = 0; while ( !s.empty() ) { arr[ j ] = s.top(); s.pop(); ++j; } arr[ i ] = '\0'; str = arr; } auto reversedata_2( string& str ) -> void { int i = 0; for ( char c = str[0]; c != '\0'; c = str[ ++i ] ); char arr[ i + 1 ]; int k = 0; for ( int j = i - 1; j >= 0; --j ) { arr[ k ] = str[ j ]; ++k; } arr[ k ] = '\0'; str = arr; } auto reversedata_3( string& str ) -> void { for ( size_t _s{ 0 }, _e{ str.size() - 1 }; _s < _e; ++_s, --_e ) { auto _c{ str[ _s ] }; str[ _s ] = str[ _e ]; str[ _e ] = _c; } } auto reversedata_4( string& str ) -> void { str = { str.crbegin(), str.crend() }; } auto reversedata_5( string& str ) -> void { reverse( str.begin(), str.end() ); } int main( int, char** ) { // reduce this number on SL, // e.g. to 10'000 constexpr size_t ITERATIONS{ 1'000'000 }; auto d1{ measure< ITERATIONS >( reversedata_1 ) }; auto d2{ measure< ITERATIONS >( reversedata_2 ) }; auto d3{ measure< ITERATIONS >( reversedata_3 ) }; auto d4{ measure< ITERATIONS >( reversedata_4 ) }; auto d5{ measure< ITERATIONS >( reversedata_5 ) }; cout << "Stack: " << d1 << " seconds\n" << "VLA: " << d2 << " seconds\n" << "Traversal: " << d3 << " seconds\n" << "Constructor: " << d4 << " seconds\n" << "Reverse: " << d5 << " seconds\n"; return EXIT_SUCCESS; }

[Q&A] Measure Reverse