package leetcode;


class Trie {
    private Trie[] children;
    //當前節點是否為一個單詞的結尾
    private boolean isEnd;
    public Trie() {
        //每個節點最多有26個字母
        children=new Trie[26];
        isEnd=false;
    }
    
    public void insert(String word) {
        Trie node=this;
        for(int i=0;i<word.length();i++) {
            
 
//找出當前字元的下標
            int index=word.charAt(i)-'a';
            if(node.children[index]==null) {
                node.children[index]=new Trie();
            }
            //指向下一個節點
            node=node.children[index];
        }
        node.isEnd=true;
    }
    
    //字首不為空，且為最後一個字元
    public boolean
 
 search(String word) {
        Trie node=SearchPrefix(word);
        return node!=null&&node.isEnd;
    }
    
    
    public boolean startsWith(String prefix) {
        Trie node=SearchPrefix(prefix);
        return node!=null;
    }
    
    //判斷是否有字首
    public Trie SearchPrefix(String prefix) {
        Trie node
 
=this;
        for(int i=0;i<prefix.length();i++) {
            int index=prefix.charAt(i)-'a';
            if(node.children[index]==null) {
                return null;
            }
            node=node.children[index];
        }
        return node;
    }
}