［leetcode刷题笔记］Implement Trie (Prefix Tree)

题目链接

一A，开森～

ac代码：

 class TrieNode {
     // Initialize your data structure here.
     char content;
     boolean isWord;
     int count;
     LinkedList<TrieNode> childList;

     public TrieNode(char c) {
         content = c;
         isWord = false;
         count = 0;
         childList = new LinkedList<TrieNode>();
     }
     public TrieNode() {
         content = ' ';
         isWord = false;
         count = 0;
         childList = new LinkedList<TrieNode>();
     }

     public TrieNode findChildC(char c){
         if(childList != null){
             for(TrieNode eachChild:childList){
                 if(eachChild.content == c)
                     return eachChild;
             }
         }
         return null;
     }
 }

 public class Trie {
     private TrieNode root;

     public Trie() {
         root = new TrieNode();

     }

     // Inserts a word into the trie.
     public void insert(String word) {
         //if already has this word
         if(search(word) == true)
             return;

         TrieNode current = root;
         for(int i = 0;i < word.length();i++){
             TrieNode child = current.findChildC(word.charAt(i));
             if(child == null){
                 TrieNode temp = new TrieNode(word.charAt(i));
                 current.childList.add(temp);
                 current = temp;
             }else{
                 current = child;
             }
             current.count++;
         }
         current.isWord = true;
     }

     // Returns if the word is in the trie.
     public boolean search(String word) {
         TrieNode current = root;
         for(int i = 0;i < word.length();i++){
             TrieNode child = current.findChildC(word.charAt(i));
             if(child == null)
                 return false;
             else{
                 current = child;
                 continue;
             }
         }
         if(current.isWord)
             return true;
         return false;
     }

     // Returns if there is any word in the trie
     // that starts with the given prefix.
     public boolean startsWith(String prefix) {
         TrieNode current = root;
         for(int i = 0;i < prefix.length();i++){
             TrieNode child = current.findChildC(prefix.charAt(i));
             if(child == null)
                 return false;
             else{
                 current = child;
                 continue;
             }
         }
         return true;
     }
 }

 // Your Trie object will be instantiated and called as such:
 // Trie trie = new Trie();
 // trie.insert("somestring");
 // trie.search("key");