[leetcode]208. Implement Trie (Prefix Tree)

题目链接：https://leetcode.com/problems/implement-trie-prefix-tree/tabs/description

 

Implement a trie with insert, search, and startsWith methods.

Note:
You may assume that all inputs are consist of lowercase letters a-z.

 

 

 

class TrieNode{
public:
    TrieNode* next[26];
    bool is_word;

    TrieNode(bool b=false)
    {
        memset(next,0,sizeof(next));
        is_word=b;
    }
};

class Trie {
public:
    /** Initialize your data structure here. */
    Trie() {
        root=new TrieNode();
    }

    /** Inserts a word into the trie. */
    void insert(string word) {
        TrieNode* p=root;
        for(int i=0;i<word.size();i++)
        {
            if(p->next[word[i]-'a']==NULL)
                p->next[word[i]-'a']=new TrieNode();
            p=p->next[word[i]-'a'];
        }
        p->is_word=true;
    }

    /** Returns if the word is in the trie. */
    bool search(string word) {
        TrieNode* p=find(word);
        return p!=NULL && p->is_word;
    }

    /** Returns if there is any word in the trie that starts with the given prefix. */
    bool startsWith(string prefix) {
        return find(prefix)!=NULL;
    }
private:
    TrieNode* root;
    TrieNode* find(string key)
    {
        TrieNode* p=root;
        for(int i=0;i<key.size() && p!=NULL;i++)
            p=p->next[key[i]-'a'];
        return p;
    }
};