Implement Trie (Prefix Tree)

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

Example:

Trie trie = new Trie();

trie.insert("apple");
trie.search("apple");   // returns true
trie.search("app");     // returns false
trie.startsWith("app"); // returns true
trie.insert("app");   
trie.search("app");     // returns true

Note:

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

• All inputs are guaranteed to be non-empty strings.

class TrieNode{
    private TrieNode[] links;
    private final int R = 26;
    private boolean isEnd;
    
    public TrieNode(){
        links = new TrieNode[26];
    }
    
    public boolean containsKey(char ch){
        return links[ch - 'a'] != null;
    }
    
    public TrieNode get(char ch){
        return links[ch - 'a'];
    }
    
    public void put(char ch, TrieNode node){
        links[ch - 'a'] = node;
    }
    
    public void setEnd(){
        isEnd = true;
    }
    
    public boolean isEnd(){
        return isEnd;
    }
}



class Trie {
    
    private TrieNode root;
    /** Initialize your data structure here. */
    public Trie() {
        root = new TrieNode();
    }
    
    /** Inserts a word into the trie. */
    public void insert(String word) {
        TrieNode node = root;
        
        for(char c : word.toCharArray()){
            if(!node.containsKey(c)){
                node.put(c,new TrieNode());
            }
            
            node = node.get(c);
        }
        
        node.setEnd();
    }
    
    /** Returns if the word is in the trie. */
    public boolean search(String word) {
        TrieNode node = searchPrifix(word);
        
        return node != null && node.isEnd();
    }
    
    public TrieNode searchPrifix(String word){
        TrieNode node = root;
        
        for(char c : word.toCharArray()){
            if(node.containsKey(c)){
                node = node.get(c);
            }else{
                return null;
            }
        }
        
        return node;
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    public boolean startsWith(String prefix) {
        TrieNode node = searchPrifix(prefix);
        
        return node != null;
    }
}

/**
 * Your Trie object will be instantiated and called as such:
 * Trie obj = new Trie();
 * obj.insert(word);
 * boolean param_2 = obj.search(word);
 * boolean param_3 = obj.startsWith(prefix);
 */