#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cctype>
#include <sstream>
 
// invariant: line_sz > length of any single word
std::vector<std::string> split( std::string str, std::size_t line_sz )
{
    if( std::all_of( std::begin(str), std::end(str), [] ( char c ) { return std::isspace(c) ; } ) )
        return {} ; // empty string or string with all spaces, return an empty vector
 
    std::vector<std::string> result(1) ; // vector containing one empty string
 
    std::istringstream stm(str) ; // use a string stream to split on white-space
    std::string word ;
    while( stm >> word ) // for each word in the string
    {
        // if this word will fit into the current line, append the word to the current line
        if( ( result.back().size() + word.size() ) <= line_sz ) result.back() += word + ' ' ;
 
        else
        {
            result.back().pop_back() ; // remove the trailing space at the end of the current line
            result.push_back( word + ' ' ) ; // and place this new word on the next line
        }
    }
 
    result.back().pop_back() ; // remove the trailing space at the end of the last line
    return result ;
}
 
int main()
{
    const std::string str = "I need to write something that passes a value from! one program to another. "
                            "This is a test (with a 20 character word) - ottffssentettffssent - end test." ;
 
 
    for( auto line : split( str, 25 ) ) std::cout << line << '\n' ;
}

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Writing the rough draft is a transition, one that takes you from the mental aspect of note taking, outlining and prewriting to.