LeetCode——Implement Trie (Prefix Tree)

Description：

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

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

实现一个简单的Trie树，参考我的博客：http://www.cnblogs.com/wxisme/p/4876197.html

 class TrieNode {
     public TrieNode[] son;
     public boolean isEnd;
     // Initialize your data structure here.
     public TrieNode() {
         this.son = new TrieNode[26];
         isEnd = false;

     }
 }

 public class Trie {
     private TrieNode root;

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

     // Inserts a word into the trie.
     public void insert(String word) {
         char[] wordChars = word.toCharArray();
         TrieNode node = this.root;
         for(char ch : wordChars) {
             int pos = ch - 'a';
             if(node.son[pos] == null) {
                 node.son[pos] = new TrieNode();
             }
             node = node.son[pos];
         }
         node.isEnd = true;
     }

     // Returns if the word is in the trie.
     public boolean search(String word) {
         char[] wordChars = word.toCharArray();
         TrieNode node = this.root;
         for(char ch : wordChars) {
             int pos = ch - 'a';
             if(node.son[pos] == null) {
                 return false;
             }
             node = node.son[pos];
         }
         return node.isEnd;
     }

     // Returns if there is any word in the trie
     // that starts with the given prefix.
     public boolean startsWith(String prefix) {

         char[] prefixChars = prefix.toCharArray();
         TrieNode node = this.root;
         for(char ch : prefixChars) {
             int pos = ch - 'a';
             if(node.son[pos] == null) {
                 return false;
             }
             node = node.son[pos];
         }
         return true;
     }
 }

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