Java

class Trie {
    private boolean isEnd;
    private Trie[] next;
    /** Initialize your data structure here. */
    public Trie() {
        isEnd = false;
        next = new Trie[26];
    }
    
    /** Inserts a word into the trie. */
    public void insert(String word) {
        if (word == null || word.length() == 0) return;
        Trie curr = this;
        char[] words = word.toCharArray();
        for (int i = 0;i < words.length;i++) {
            int n = words[i] - 'a';
            if (curr.next[n] == null) curr.next[n] = new Trie();
            curr = curr.next[n];
        }
        curr.isEnd = true;
    }
    
    /** Returns if the word is in the trie. */
    public boolean search(String word) {
        Trie node = searchPrefix(word);
        return node != null && node.isEnd;
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    public boolean startsWith(String prefix) {
        Trie node = searchPrefix(prefix);
        return node != null;
    }

    private Trie searchPrefix(String word) {
        Trie node = this;
        char[] words = word.toCharArray();
        for (int i = 0;i < words.length;i++) {
            node = node.next[words[i] - 'a'];
            if (node == null) return null;
        }
        return node;
    }
}

Python

class Trie(object):
  
	def __init__(self): 
		self.root = {} 
		self.end_of_word = "#" 
 
	def insert(self, word): 
		node = self.root 
		for char in word: 
			node = node.setdefault(char, {}) 
		node[self.end_of_word] = self.end_of_word 
 
	def search(self, word): 
		node = self.root 
		for char in word: 
			if char not in node: 
				return False 
			node = node[char] 
		return self.end_of_word in node 
 
	def startsWith(self, prefix): 
		node = self.root 
		for char in prefix: 
			if char not in node: 
				return False 
			node = node[char] 
		return True

JavaScript

class Trie {
  constructor() {
    this.root = {};
    this.endOfWord = "$";
  }

  insert(word) {
    let node = this.root;
    for (let ch of word) {
      node[ch] = node[ch] || {};
      node = node[ch];
    }
    node[this.endOfWord] = this.endOfWord;
  }

  search(word) {
    let node = this.root;
    for (let ch of word) {
      if (!node[ch]) return false;
      node = node[ch];
    }
    return node[this.endOfWord] === this.endOfWord;
  }

  startsWith(word) {
    let node = this.root;
    for (let ch of word) {
      if (!node[ch]) return false;
      node = node[ch];
    }
    return true;
  }
}


let trie = new Trie();
console.log(trie.insert("apple"));
console.log(trie.search("apple")); // 返回 true
console.log(trie.search("app")); // 返回 false
console.log(trie.startsWith("app")); // 返回 true
console.log(trie.insert("app"));
console.log(trie.search("app")); // 返回 true

C/C++

class Trie {
    struct TrieNode {
        map<char, TrieNode*>child_table;
        int end;
        TrieNode(): end(0) {}
    };
        
public:
    /** Initialize your data structure here. */
    Trie() {
        root = new TrieNode();
    }
    
    /** Inserts a word into the trie. */
    void insert(string word) {
        TrieNode *curr = root;
        for (int i = 0; i < word.size(); i++) {
            if (curr->child_table.count(word[i]) == 0)
                curr->child_table[word[i]] = new TrieNode();
                
            curr = curr->child_table[word[i]];                
        }
        curr->end = 1;
    }
    
    /** Returns if the word is in the trie. */
    bool search(string word) {
        return find(word, 1);
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    bool startsWith(string prefix) {
        return find(prefix, 0);
    }
private:
    TrieNode* root;
    bool find(string s, int exact_match) {
        TrieNode *curr = root;
        for (int i = 0; i < s.size(); i++) {
            if (curr->child_table.count(s[i]) == 0)
                return false;
            else
                curr = curr->child_table[s[i]];
        }
        
        if (exact_match)
            return (curr->end) ? true : false;
        else
            return true;
    }
};