leetcode Implement Trie (Prefix Tree)

好几个月之前面Amazon的时候，跪在了Trie树的问题，又联想到一个在微软实习过得朋友说他mentor告诉他手写trie是一个很基本的基本功，本想在LC上AC下这道题目，期间毕业论文各种杂事，一个拖延症能拖好几个月。所幸今天在家抽出了时间来写这段代码。言归正传，关于前缀树的定义，资料很多，根据这些资料翻译成对应的代码，下面给出AC的代码：

class Trie {public:    /** Initialize your data structure here. */    Trie() {        root = new TrieNode; //初始化根节点        }    /** Inserts a word into the trie. */    void insert(string word) {        TrieNode* cur = root; //当前的节点是根节点        for(int i = 0; i < word.length(); ++i)        {            int k = (word[i] - 'a');            if(cur -> next[k] == NULL)            {                cur -> next[k] = new TrieNode();            }            cur = cur -> next[k];        }        cur -> exsit = true;    }    /** Returns if the word is in the trie. */    bool search(string word) {        TrieNode* cur = root;        for(int i = 0; i < word.length(); ++i)        {            int k = word[i] - 'a';            if(cur -> next[k] == NULL)                return false;            cur = cur -> next[k];        }        if(cur -> exsit)            return true;        else             return false;    }    /** Returns if there is any word in the trie that starts with the given prefix. */    bool startsWith(string prefix) {        TrieNode* cur = root;        for(int i = 0; i < prefix.length(); ++i)        {            int k = prefix[i] - 'a';            if(cur -> next[k] == NULL)                return false;            cur = cur -> next[k];        }        return true;    }    struct TrieNode    {        TrieNode* next[26];        bool exsit;        TrieNode() : exsit(false)        {            memset(next, 0, sizeof(next));        }    };    TrieNode* root;};/** * 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); */