leetcode 208 实现 Trie (前缀树)

class Trie {
public:
    /** Initialize your data structure here. */
    Trie() {
        is_str_end = false;
        for(int i=0; i<26; i++)
            next[i] = NULL;
    }
    
    /** Inserts a word into the trie. */
    void insert(string word) {
        Trie *p = this;
        for(int i=0; i<word.length(); i++)
        {
            if((p->next)[word[i] - ‘a‘] == NULL)
            {
                Trie *q = new Trie();
                (p->next)[word[i] - ‘a‘] = q;
            }
            p = (p->next)[word[i] - ‘a‘];
        }
        p->is_str_end = true;
    }
    
    /** Returns if the word is in the trie. */
    bool search(string word) {
        Trie *p = this;
        for(int i=0; i<word.length(); i++)
        {
            if((p->next)[word[i] - ‘a‘] == NULL)
                return false;
            p = (p->next)[word[i] - ‘a‘];
        }
        if(p->is_str_end == false)
            return false;
        return true;
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    bool startsWith(string prefix) {
        Trie *p = this;
        for(int i=0; i<prefix.length(); i++)
        {
            if((p->next)[prefix[i] - ‘a‘] == NULL)
                return false;
            p = (p->next)[prefix[i] - ‘a‘];
        }
        return true;
    }
private:
    bool is_str_end;
    Trie* next[26];
};

/**
 * 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);
 */