백준 1316번: 그룹 단어 체커

문제 출처: https://www.acmicpc.net/problem/1316

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
 
public class Main {
    
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        int N = Integer.parseInt(reader.readLine());
        int result = 0;
        
        for(int i=0 ; i<N ; i++){
            String str = reader.readLine();
            ArrayList<Character> strList = new ArrayList<>();  
            
            for(int j=0 ; j<str.length() ; j++){
                if(strList.contains(str.charAt(j)) && strList.get(strList.size()-1) != str.charAt(j)){
                    break;
                }
                else {
                    strList.add(str.charAt(j));
                    if(j==str.length()-1)
                        result++;
                }
            }
        }
    
        System.out.println(result);
    }
}