C++ Function Parameter Using a reference parameter

#include <iostream>
#include <iomanip>
#include <string>
#include <vector>

using std::string;
using std::vector;
void find_words(vector<string>& words, string& str, const string& separators);
void list_words(const vector<string>& words);

int main()//ww w.  jav a2s  .  com
{
  string text;                                               // The string to be searched
  std::cout << "Enter some text terminated by *:\n";
  std::getline(std::cin, text, '*');

  const string separators {" ,;:.\"!?'\n"};                  // Word delimiters
  vector<string> words;                                      // Words found

  find_words(words, text, separators);
  list_words(words);
}

void find_words(vector<string>& words, string& str, const string& separators)
{
  int start {str.find_first_not_of(separators)};          // First word start index
  int end {};                                             // Index for end of a word

  while (start != string::npos)                              // Find the words
  {
    end = str.find_first_of(separators, start + 1);          // Find end of word
    if (end == string::npos)                                 // Found a separator?
      end = str.length();                                    // No, so set to last + 1
    words.push_back(str.substr(start, end - start));         // Store the word
    start = str.find_first_not_of(separators, end + 1);      // Find 1st character of next word
  }
}

void list_words(const vector<string>& words)
{
  std::cout << "Your string contains the following " << words.size() << " words:\n";
  int count {};                                           // Number output
  for (const auto& word : words)
  {
    std::cout << std::setw(15) << word;
    if (!(++count % 5))
      std::cout << std::endl;
  }
  std::cout << std::endl;
}