1032. Stream of Characters

StreamChecker.cpp

struct Node {
    Node* children[26];
    int flag;
    
    Node() {
        memset(children, 0, sizeof(children));
        flag = 0;
    }
};

class StreamChecker {
    Node* root = nullptr;
    std::unordered_set<Node*> s, tmp_s;
    std::string target;
public:
    StreamChecker(vector<string>& words) {
        root = new Node();
        for (auto& word : words) {
            std::reverse(word.begin(), word.end());
            auto p = root;
            for (auto c : word) {
                if (p->children[c-'a'] == nullptr) {
                    p->children[c-'a'] = new Node();
                }
                p = p->children[c-'a'];
            }
            p->flag = 1;
        }
        s.reserve(2000);
        tmp_s.reserve(2000);
    }
    
    bool query(char letter) {
        target.push_back(letter);
        auto cur = root;
        for (int i = target.size() - 1; i >= 0; --i) {
            auto c = target[i];
            if (cur->children[c-'a'] == nullptr) {
                return false;
            } else {
                cur = cur->children[c-'a'];
                if (cur->flag == 1) {
                    return true;
                }
            }   
        }
        return false;
    }
};

/**
 * Your StreamChecker object will be instantiated and called as such:
 * StreamChecker* obj = new StreamChecker(words);
 * bool param_1 = obj->query(letter);
 */