Java 代码

使用树来表示，理解起来更简单

import java.io.BufferedInputStream;
import java.util.*;
public class Main{
    public static void main(String [] args){
        Scanner sc = new Scanner(new BufferedInputStream(System.in));
        int n = sc.nextInt();
        sc.nextLine();
        Trie trie = new Trie();
        for(int i=0;i<n;i++){
            String str = sc.nextLine();
            //System.out.println(str);
            String [] strs = str.split(" ");
            if("I".equals(strs[0])){
                trie.insert(strs[1]);
            }else{
                int res = trie.query(strs[1]);
                System.out.println(res);
            }
        }

    }

}
class Trie{
    private TreeNode root = new TreeNode();
    public void insert(String str){
        char [] chars = str.toCharArray();
        TreeNode p = root;
        for(int i=0;i<chars.length;i++){
            int index = chars[i] - 'a';
            if(p.children[index]==null){
                TreeNode node = new TreeNode();
                p.children[index] = node;
            }
            p = p.children[index];
        }
        p.endCount++;

    }
    public int query(String str) {
        char [] chars = str.toCharArray();
        TreeNode p = root;
        for(int i=0;i<chars.length;i++){
            int index = chars[i] - 'a';
            if(p.children[index]==null){
                return 0;
            }
            p = p.children[index];
        }
        return p.endCount;
    }

}
class TreeNode{
    int endCount = 0;
    TreeNode[] children = new TreeNode[26];
}