Solution.cpp

class Trie {
private:
    vector<Trie*> children;
    bool isEnd;

    Trie* searchPrefix(string s) {
        Trie* node = this;
        for (char c : s) {
            int idx = c - 'a';
            if (!node->children[idx]) return nullptr;
            node = node->children[idx];
        }
        return node;
    }

public:
    Trie()
        : children(26)
        , isEnd(false) {}

    void insert(string word) {
        Trie* node = this;
        for (char c : word) {
            int idx = c - 'a';
            if (!node->children[idx]) node->children[idx] = new Trie();
            node = node->children[idx];
        }
        node->isEnd = true;
    }

    bool search(string word) {
        Trie* node = searchPrefix(word);
        return node != nullptr && node->isEnd;
    }

    bool startsWith(string prefix) {
        Trie* node = searchPrefix(prefix);
        return node != nullptr;
    }
};

/**
 * Your Trie object will be instantiated and called as such:
 * Trie* obj = new Trie();
 * obj->insert(word);
 * bool param_2 = obj->search(word);
 * bool param_3 = obj->startsWith(prefix);
 */