void noPrefix(vector<string> words) {
    unordered_set<string_view> prefix_set, word_set;
    
    // iterate over all words, using references is crucial for unordered_set<string_view> to work
    for (const auto& w : words) {
        auto word_sv = string_view(w);
        
        // check if current word w is a prefix of any previous word
        if (prefix_set.count(word_sv)) {
            printf("BAD SET\n%s\n", w.c_str());
            return;
        }
        
        // iterate over all possible non-empty prefixes of current word w
        for (auto size=1u; size<=w.size(); size++) {
            auto word_prefix_sv = word_sv.substr(0, size);
            
            // check if any previous word is a prefix of current word w
            if (word_set.count(word_prefix_sv)) {
                printf("BAD SET\n%s\n", w.c_str());
                return;
            }
            
            // update prefix set
            prefix_set.insert(word_prefix_sv);
        }
        
        // update word_set
        word_set.insert(word_sv);
    }
    
    printf("GOOD SET\n");
}