Подсчитывать количество цифр 2 - C++ - Ответ 3961869

using namespace std;
// ---------------------------------------------------------------------------
typedef unsigned __int64 ull; // a long, long unsigned value
// ---------------------------------------------------------------------------
ull straight_count_2( ull n ) {
    ull cnt = 0;
 
    for ( ull i = 0, j; i <= n; ++i ) {
        for ( j = i; j != 0; j /= 10 ) {
            if ( j % 10 == 2 ) {
                ++cnt;
            }
        }
    }
    return cnt;
}
// ---------------------------------------------------------------------------
struct thread_data {
    ull begin, end, result;
};
DWORD WINAPI thread_count( LPVOID lpParam ) {
    thread_data *data = ( thread_data* )lpParam;
    ull cnt = 0, end = data->end;
 
    for ( ull i = data->begin, j; i <= end; ++i ) {
        for ( j = i; j != 0; j /= 10 ) {
            if ( j % 10 == 2 ) {
                ++cnt;
            }
        }
    }
    data->result = cnt;
}
ull do_threaded_count( int _threads_amount, ull _seed ) {
    HANDLE *threads = new HANDLE[_threads_amount];
    thread_data *data = new thread_data[_threads_amount];
    ull result = 0, seed_part = _seed / _threads_amount;
 
    for ( size_t i = 0; i < _threads_amount; ++i ) {
        data[i].begin = seed_part * i + 1;
        data[i].end = seed_part * ( i + 1 );
        threads[i] = CreateThread( NULL, 0, &thread_count, &data[i], 0, NULL );
    }
    WaitForMultipleObjects( _threads_amount, threads, TRUE, INFINITE );
 
    for ( size_t i = 0; i < _threads_amount; result += data[i].result, CloseHandle( threads[i] ), ++i );
    delete[]threads;
    delete[]data;
 
    return result;
}
// ---------------------------------------------------------------------------
int _tmain( int argc, _TCHAR *argv[] ) {
    system( "color 2e" ); 
    system( "chcp 1251" );
    system( "cls" );
    //////////////////////////////////////
    t_time_counter tc;
    ull result, seed = 50000000;
 
    tc.start( );
    result = straight_count_2( seed );
    tc.stop( );
    cout << "straight_count_2() elapsed " << tc.mins << ":" << tc.secs << ":" << tc.msecs <<
                   ",  result = " << result << endl;
 
    for ( size_t i = 2; i <= 20; i += 2 ) {
        tc.start( );
        result = do_threaded_count( i, seed );
        tc.stop( );
        cout << i << " threads count elapsed " << tc.mins << ":" << tc.secs << ":" << tc.msecs <<
                       ",  result = " << result << endl;
    }
 
    //////////////////////////////////////
    cout << "\n\n";
    system( "pause" );
    return 0;
}

class t_time_counter {
public:
    DWORD full_time;
    int hours, mins, secs, msecs;
    void __fastcall start( ) {
        full_time = GetTickCount( );
    }
    void __fastcall stop( ) {
        full_time = GetTickCount( ) - full_time;
        hours = ( mins = ( secs = full_time / 1000 ) / 60 ) / 60;
        mins %= 60;
        secs %= 60;
        msecs = full_time % 1000;
    }
};