Считать с клавиатуры текст и вывести на экран только предложения, состоящие из заданного количества слов

#include <iostream>
#include <boost/algorithm/string.hpp>
#include <string>
#include <vector>
#include <algorithm>
#include <iterator>
 
int main()
{
   std::string s = "Hello and what. Is it now true? Such good thing! What is it?!";
   const size_t words_count = 3;
   const std::string sent_delims = ".?!";
   const std::string word_delims = " ,:";
   std::vector<std::string> sentences;
   boost::split(sentences, s, boost::is_any_of(sent_delims), boost::token_compress_on);
   std::transform(sentences.begin(), sentences.end(), sentences.begin(), [](const std::string& val)
   {
      return boost::trim_copy(val);
   });
   std::vector<std::string> right_sentences;
   std::copy_if(sentences.begin(), sentences.end(), std::back_inserter(right_sentences),
   [words_count, word_delims](const std::string& value) -> bool
   {
      std::vector<std::string> words;
      boost::split(words, value, boost::is_any_of(word_delims), boost::token_compress_on);
      return words.size() == words_count;
   });
   std::copy(right_sentences.begin(), right_sentences.end(), 
   std::ostream_iterator<std::string>(std::cout, "\n"));
}

#include <iostream>
#include <string>
#include <algorithm>
 
int main()
{
   std::string s = "Hello and what. Is it now true? Such good thing! What is it?!";
   char symbol = 'T';
   std::string::iterator iter = std::find(s.begin(), s.end(), symbol);
   if (iter == s.end())
   {
      std::cout << "No symbol " << symbol << " in string." << std::endl;
   }
   else
   {
      s.erase(iter);
   }
   s.insert(s.begin(), 1, symbol);
   std::cout << "string: " << s << " symbol: " << symbol << std::endl;
}

#include <iostream>
using namespace std;
 
struct Sent{
int count;
int pos;
Sent():count(0),pos(0){
}
};
 
int main(){
    Sent sent[20];
    int val = 0;
char text[] ="Spring is green. Summer is brigth. Autumn now. August." ;
 
size_t i = 0;
size_t j = 0;
size_t n = 0;
size_t k = 0;
bool loop = false;
cout << "How much words?:   ";
cin >> val;
    while(text[i]){
    if(isalpha(text[i])&&!isalpha(text[i + 1])){
        sent[j].count++;
    
    }
        if(text[i] == '.'){
            sent[j].pos = i;
            j++;}
        
    i++;}
j = 0;
i = 0;
     while(text[i]) {   
        
         if( text[i] == '.'&& sent[j].count == val && sent[j].pos == i) {   
             for (k = n; k <= i; k++) cout <<  text[k];
             n = i + 1;loop = true;
         }
        
         if( text[i] == '.'&& sent[j].count != val )  {   
             
             n = i + 2;
         }
            
          if( text[i] == '.') j++;
 
          i ++;
     }
     if(!loop) cout << "Not found";
     cout << endl;
system("pause");
}

n = i + 2;

n = i + 1;