函数 sort，unique，stable_sort，count_if，谓词

bool isShorter(const string &s1,const string &s2)
{
    return s1.size() < s2.size();                              
}

bool GT6(const string &s)
{
    return s.size() >= 6;
}

int main()
{
    vector<string> words;
    string nect_word;
    while (cin >> next_word){
        words.push_back(next_word);
　　}    
    sort (words.begin(), words.end());
    vector<string>::iterator end_unique = unique(words.begin(), words.end());
    words.erase(end_unique, words.end());
    stable_sort(words.begin(),word.end(),isShorter);
    vector<string>::size_type wc = count_if (words.begin(), words.end(), GT6);
    cout << wc << " " << make_plural (wc, "word", "s") << " 6 characters or longer " << endl;
    return 0;
}