[백준][Java] 4949번 균형잡힌 세상 (String, stack)

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.Stack;
 
 
public class Main {
        
    private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
    
    private static String check(String input) {
        
        Stack<Character> st = new Stack<>();
        for(int i=0; i<input.length()-1; i++) {
            if(input.charAt(i)=='(') st.push('(');
            else if(input.charAt(i)=='[') st.push('[');
            else if(input.charAt(i)==')') {
                if(st.isEmpty() || st.peek()!='(') return "no";
                else {
                    st.pop();
                }
            }
            else if(input.charAt(i)==']') {
                if(st.isEmpty() || st.peek()!='[') return "no";
                else {
                    st.pop();
                }
            }
        }
        
        if(st.isEmpty()) return "yes";
        else return "no";
    }
    
    public static void main(String[] args) throws IOException{
        
        StringBuilder sBuilder = new StringBuilder();
        
        while(true) {
            String input = br.readLine();
            if(input.equals(".")) break;
            
            sBuilder.append(check(input)+"\n");
        }
        
        
        bw.write(sBuilder.toString()); 
        
        
        bw.flush(); 
        bw.close();
    }
}