PTA jmu-Java-m06 统计一篇英文文章中出现的不重复单词的个数分数 12

输入一篇英文文章，碰到"!!!!!"的时候停止，输出文章中出现的不重复单词的个数(注意：单词不区分大小写，如：The和the为一个单词)

输入格式:

一篇英文文章，以"!!!!!"结尾

输出格式:

不重复单词的个数

输入样例:

Unmanned aerial vehicles have been adopted in the inspection of violations Procurators will file public interest litigations against perpetrators who will need to replant trees take down illegal buildings control pollution and compensate environment-related losses  
The Yellow River is the second longest river in China It originates in the northwestern province of Qinghai and runs through nine provinces and autonomous regions in western central north and eastern China  
!!!!!

输出样例:

55

代码长度限制16 KB

时间限制800 ms

内存限制64 MB

import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        ArrayList<String> list = new ArrayList<>();
        while(true){
            String str = sc.next().toLowerCase();
            if(str.equals("!!!!!")) break;
            //若lisi中没有str返回-1，来判断是否以添加过单词
            if(list.indexOf(str) == -1){
                list.add(str);
            }
        }
        System.out.println(list.size());
    }
}