Улучшение алгоритма подсчета строк, букв, слов

#include <iostream>
using namespace std;
 
int main ()
{  
char ch;
  cout <<"enter your text: " ;
  cin >> ch; 
    int numChars = 0; 
    int numLines = 0;
    int numWords = 0;
    while ((ch=getchar())!= 4) // Keyboard input will continue until "ASCII value 4 + <enter>" (CTRL+D+<enter>) will be entered
        switch (ch)
             {      
    case  ' ' : numWords++; break; // The condition of the definition of words
    case '\t' : numWords++; break; // The condition of the definition of words
    case '\n' : numWords++; numLines++; break; // The condition of the definition of words and newlines 
    default   : numChars++; break;       
            }
    numLines += 1; // for some reason it needs to add one and the results are correct
 cout << "CharCounter results: " << numChars << endl;
 cout << "WordsCounter results: " << numWords << endl;
 cout << "LinesCounter results: " << numLines << endl;
    return 0;
}

#include <iostream>
using namespace std;
 
int main ()
{  
char ch;
  cout <<"Enter your text: " ;
    int numChars = 0; 
    int numLines = 0;
    int numWords = 0;
    int spaceFlag = 1;
    while ((ch=getchar())!= 4)
    switch (ch)
    {      
    case '\n': numLines++;
    case '\t': case ' ': if (!spaceFlag) numWords++; spaceFlag = 1; break;
    default: numChars++; spaceFlag = 0; break;      
    }
    numLines += 1;
    if (!spaceFlag) numWords++;
 cout << "CharCounter results: " << numChars << endl;
 cout << "WordsCounter results: " << numWords << endl;
 cout << "LinesCounter results: " << numLines << endl;
 system("pause");
    return 0;
}

#include <iostream>
using namespace std;
 
int main ()
{  
    char ch;
    cout <<"Enter your text: " ;
    int numChars = 0; 
    int numLines = 0;
    int numWords = 0;
    int spaceFlag = 0;
    while ((ch=getchar())!= 4)
        switch (ch)
        {      
        case '\n': numLines++;
        case '\t':
                case ' ': spaceFlag=1; break;
        default: 
            numChars++; 
            if (spaceFlag==1)
            {
                ++numWords;
                spaceFlag=0;
            }
        }
    numLines += 1;
    cout << "CharCounter results: " << numChars << endl;
    cout << "WordsCounter results: " << numWords << endl;
    cout << "LinesCounter results: " << numLines << endl;
    system("pause");
    return 0;
}

    int numChars = 0; 
    int numLines = 0;
    int numWords = 0;
    int spaceFlag = 0;

int spaceFlag = 1;

#include <string>
#include <vector>
#include <iostream>
 
#include <boost/algorithm/string.hpp>
 
int main()
{
   std::string some_string = "Hello\n and what do you\t now\n";
   std::vector<std::string> lines;
   boost::split(lines, some_string, boost::is_any_of("\n"), boost::token_compress_on);
   std::transform(lines.begin(), lines.end(), lines.begin(), [](const std::string& line)
   {
      return boost::trim_copy(line);
   });
   lines.erase(std::remove_if(lines.begin(), lines.end(), [](const std::string& line) 
   { 
      return line.empty(); 
   }), lines.end());
   std::vector<std::string> words;
   std::for_each(lines.begin(), lines.end(), [&words] (const std::string& line)
   {
      std::vector<std::string> temp;
      boost::split(temp, line, boost::is_any_of("\t "), boost::token_compress_on);
      words.insert(words.end(), temp.begin(), temp.end());
   });
   std::cout << "Lines: " << lines.size() << " words: " << words.size() <<
      " letters: " << std::accumulate(words.begin(), words.end(), 0, [](const int total, const std::string& value)
      {
         return total + value.length();
      }) << std::endl;
}

//
//
#include <iostream>
using namespace std;
char ch;
 
int main ()
{
  
  cout <<"enter your text: " ;
  cin >> ch; 
 
 
    int numChars = 0; 
    int numLines = 0;
    int numWords=0;
    int spaceFlag = 1;
 
    do
    {
        
 
     if(ch == '\n')
             {
       numLines++; // increase the count of lines by one if ch IS '\n'
             }
 
     if (ch == ' ') // The condition of the definition of words           
         spaceFlag = 1 ;
 
     if (ch =='a-z'||'A-Z')
            {       
       numChars++;
                  if (spaceFlag==1) 
                   {
                 ++numWords;
                 spaceFlag=0;
                   }
             }
 
    
 
    }
    
 
    while ((ch=getchar())!= 4);  // Keyboard input will continue until "ASCII value 4 + <enter>" (CTRL+D+<enter>) will be entered
 
numLines += 1; // for some reason it needs to add one and the results are correct 
 
 cout << "CharCounter results: " << numChars;
 cout << endl;
 
 cout <<"WordsCounter results: " << numWords;
 cout << endl;
 
 cout <<"LinesCounter results: " << numLines;
 cout << endl;
 
  
  return 0;
}