#include <string>
#include <iostream>
#include <boost/tokenizer.hpp>
 
void split_and_show(const std::string& s)
{
    typedef boost::tokenizer<boost::char_separator<char> > tok_t;
    boost::char_separator<char> sep(" ", "", boost::keep_empty_tokens);
    tok_t tok(s, sep);
    for(tok_t::iterator i = tok.begin(); i!=tok.end(); ++i)
            std::cout << '"' << *i << "\"\n";
}
int main()
{
    split_and_show("This is a string");
    split_and_show("This  is a string");
}

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