[JAVA/SWEA] 3135: 홍준이의 사전놀이

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import java.util.*;
/**
 *
 * @author HEESOO
 *
 */
 public class UserSolution {
    static Trie[] tries;
    public void init() {
        tries=new Trie[26];
    }
    
    public void insert(int buffer_size, String buf) {
        int root=buf.charAt(0)-'a';
        if(tries[root]==null) tries[root]=new Trie();
        tries[root].insert(buf);
    }
    
    public int query(int buffer_size, String buf) {
        int root=buf.charAt(0)-'a';
        if(tries[root]==null) return 0;
        return tries[root].getCnt(buf);
    }
}

class Trie{
    Node root;
    public Trie() {
        this.root=new Node();
    }
    public void insert(String word) {
        Node node=root;
        for(int i=0;i<word.length();i++) {
            node=node.children.computeIfAbsent(word.charAt(i), c->new Node());
            node.cnt++;
        }
    }
    
    public int getCnt(String query) {
        Node node=root;
        for(int i=0;i<query.length();i++) {
            if(!node.children.containsKey(query.charAt(i))) return 0;
            node=node.children.get(query.charAt(i)); 
        }
        return node.cnt;
    }
}

class Node{
    HashMap<Character, Node> children;
    int cnt;
    public Node() {
        this.children=new HashMap<>();
        this.cnt=0;
    }
}