Trie树[前缀树,字典树]

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

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

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class TrieNode {public:    // Initialize your data structure here.    TrieNode()     {        memset(child,NULL,sizeof(child));        flag=false;    }    TrieNode* child[26];    bool flag;};class Trie {public:    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->child[word[i]-'a']!=NULL)            {                p=p->child[word[i]-'a'];            }            else            {                p->child[word[i]-'a']=new TrieNode();                p=p->child[word[i]-'a'];            }        }        p->flag=true;   //表明到此处为一个字符串    }    // Returns if the word is in the trie.    bool search(string word)     {        TrieNode* p=root;        for(int i=0;i<word.size();i++)        {            if(p->child[word[i]-'a']==NULL)                return false;            p=p->child[word[i]-'a'];        }        if(p->flag)            return true;        return false;    }    // Returns if there is any word in the trie    // that starts with the given prefix.    bool startsWith(string prefix)     {        TrieNode* p=root;        for(int i=0;i<prefix.size();i++)        {            if(p->child[prefix[i]-'a']==NULL)                return false;            p=p->child[prefix[i]-'a'];        }        return true;    }private:    TrieNode* root;};// Your Trie object will be instantiated and called as such:// Trie trie;// trie.insert("somestring");// trie.search("key");

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