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");