class Trie {
private class Node{
private Node[] next;
// true代表一个单词结尾于此
private boolean hasWord;
public Node(){
next=new Node[26];
}
}
private Node root;
/** Initialize your data structure here. */
public Trie() {
root=new Node();
}
private Node insert(String w,Node n,int d){
// 为空，找到插入点
if(n==null){
n=new Node();
}
// 是否单词已经到了最后一个字母
if(d==w.length()){
n.hasWord=true;
return n;
}
// 如果还剩下字母，那么继续插入
int c=w.charAt(d)-'a';
n.next[c]=insert(w,n.next[c],d+1);
return n;
}
/** Inserts a word into the trie. */
public void insert(String word) {
root=insert(word,root,0);
}
private boolean search(String w,Node n,int d){
if(n==null){
return false;
}
if(d==w.length()){
return n.hasWord;
}
int c=w.charAt(d)-'a';
return search(w,n.next[c],d+1);
}
/** Returns if the word is in the trie. */
public boolean search(String word) {
return search(word,root,0);
}
private boolean startsWith(String w,Node n,int d){
if(n==null){
return false;
}
if(d==w.length()){
return true;
}
int c=w.charAt(d)-'a';
return startsWith(w,n.next[c],d+1);
}
/** Returns if there is any word in the trie that starts with the given prefix. */
public boolean startsWith(String prefix) {
return startsWith(prefix,root,0);
}
}
/**
* 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);
*/
