Trie

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class TrieNode {
public:
    TrieNode *next[26];
    bool isEnd;
    TrieNode() {
        for (int i = 0; i < 26; i++) next[i] = nullptr;
        isEnd = false;
    }
};

class Trie {
public:
    TrieNode *root;

    Trie() {
        root = new TrieNode();
    }

    void insert(string word) {
        int wordLen = word.size();

        TrieNode* p = root;
        for (int i = 0; i < wordLen; i++) {
            if (p->next[word[i] - 'a'] == nullptr) {
                p->next[word[i] - 'a'] = new TrieNode();
            }
            p = p->next[word[i] - 'a'];
        }
        p->isEnd = true;
    }

    bool search(string word) {
        int wordLen = word.size();
        TrieNode* p = root;

        for (int i = 0; i < wordLen; i++) {
            if (p->next[word[i] - 'a'] == nullptr) return false;

            p = p->next[word[i] - 'a'];
        }

        return p->isEnd;
    }

    bool startsWith(string prefix) {
        int wordLen = prefix.size();
        TrieNode* p = root;

        for (int i = 0; i < wordLen; i++) {
            if (p->next[prefix[i] - 'a'] == nullptr) return false;

            p = p->next[prefix[i] - 'a'];
        }

        return true;
    }
};

/**
 * 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);
 */