211. Design Add and Search Words Data Structure

class WordDictionary {
    struct TrieNode {
        TrieNode *children[26] = {nullptr};
        bool isEnd = false;
    };

    TrieNode *root = nullptr;

public:
    /** Initialize your data structure here. */
    WordDictionary() : root(new TrieNode) {

    }

    /** Adds a word into the data structure. */
    void addWord(string word) {
        auto p = root;
        for (auto c : word) {
            int k = c - 'a';
            if (!p->children[k]) {
                p->children[k] = new TrieNode;
            }
            p = p->children[k];
        }
        p->isEnd = true;
    }

    /** Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter. */
    bool search(string word) {
        return search(word, 0, root);
    }

    bool search(const string &w, int i, TrieNode *p) {
        if (!p) return false;
        if (i == w.length()) return p->isEnd;
        if (w[i] != '.') return search(w, i + 1, p->children[w[i] - 'a']);
        for (int k = 0; k < 26; ++k) {
            if (search(w, i + 1, p->children[k])) return true;
        }
        return false;
    }
};

/**
 * Your WordDictionary object will be instantiated and called as such:
 * WordDictionary* obj = new WordDictionary();
 * obj->addWord(word);
 * bool param_2 = obj->search(word);
 */