class Trie {
public:
    bool insert(string word) {
        if (!head) {
            head.reset(make_node(L'\0'));
        }
        
        bool foundPrefix = true;
        auto working = head.get();
        for (auto c : word) {
            const auto idx = c - 'a';       
            if (working->isLeaf) {
                // hit a prefix trying to insert the word
                return true;
            }
            
            if (!working->children[idx]) {
                // we are appending to the trie, so no prefix was found.
                working->children[idx].reset(make_node(c));  
                foundPrefix = false;
            }
            
            working = working->children[idx].get();
        }
        
        if (working) {
            working->isLeaf = true;
        }
        
        return foundPrefix;
    }
    
private:
    struct Node {
        char data;
        std::unique_ptr<Node> children[10];
        bool isLeaf;
    };
    
    Node* make_node(char d) {
        return new Node{ d, {}, false };
    }
    
    std::unique_ptr<Node> head{};
};

void noPrefix(vector<string> words) {
    Trie t;
    for (auto word : words) {
        if (t.insert(word))
        {
            printf("BAD SET\n");
            printf("%s\n", word.c_str());
            return;
        }
    }
    
    printf("GOOD SET\n");
}