个人认为，面试时候将Trie写成结构体方便面试官理解一点，提供一个自己的解法

class StreamChecker {
public:
    struct Trie{
        unordered_map<char,Trie*> child;
        bool flag;
    };
    string checkStr;
    Trie* root;
    void insert(string &s){
        reverse(s.begin(),s.end());
        auto cur=root;
        for (auto &c:s){
            if (!cur->child.count(c)) cur->child[c]=new Trie();
            cur=cur->child[c];
        }
        cur->flag=true;
    }
    StreamChecker(vector<string>& words) {
        root=new Trie();
        for (auto &s:words)
            insert(s);
    }

    bool query(char letter) {
        checkStr+=letter;
        auto cur=root;
        for (int i=checkStr.size()-1;i>=0;i--){
            char ch=checkStr[i];
            if (!cur->child.count(ch)) return false;
            cur=cur->child[ch];
            if (cur->flag) return true;
        }
        return false;
    }
};