208. 实现 Trie (前缀树)

主要是记录一下这个数据结构。

比如这个trie树，包含三个单词：sea，sells，she。

代码：

 class Trie {
     bool isWord;
     vector<Trie*> children;
 public:
     /** Initialize your data structure here. */
     Trie() {
         isWord=false;
         children.assign(,nullptr);
     }

     /** Inserts a word into the trie. */
     void insert(string word) {
         if(word.empty()){return;}
         auto cur=this;
         for(int i=;i<word.size();++i){
             if(cur->children[word[i]-'a']==nullptr){
                 cur->children[word[i]-'a']=new Trie();
             }
             cur=cur->children[word[i]-'a'];
         }
         cur->isWord=true;
     }

     /** Returns if the word is in the trie. */
     bool search(string word) {
         auto cur=this;
         for(int i=;i<word.size();++i){
             if(cur->children[word[i]-'a']==nullptr){
                 return false;
             }
             cur=cur->children[word[i]-'a'];
         }
         return cur->isWord;
     }

     /** Returns if there is any word in the trie that starts with the given prefix. */
     bool startsWith(string prefix) {
         auto cur=this;
         for(int i=;i<prefix.size();++i){
             if(cur->children[prefix[i]-'a']==nullptr){
                 return false;
             }
             cur=cur->children[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);
  */