백준 9012번: 괄호

문제 출처: https://www.acmicpc.net/problem/9012

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Stack;
 
public class algo4_9012_parenthesis_string {
    
    public static void main(String[] args) throws NumberFormatException, IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        StringBuilder builder = new StringBuilder();
    
        Integer T = Integer.parseInt(reader.readLine());
        
        for(int i=0 ; i<T ; i++){
            if(validPS(reader.readLine()))
                builder.append("YES\n");
            else
                builder.append("NO\n");
        }
        System.out.println(builder);
    }
    
    public static boolean validPS(String psStr){
        boolean isValid = false;
        Stack<Character> stack = new Stack<>();
        
        int position = psStr.length()-1;
        stack.push(psStr.charAt(position));
         
        for(--position ; position>=0 ; position--){
            char ps = psStr.charAt(position);
            
            if(stack.isEmpty() || ps==stack.peek())
                stack.push(ps);
            else if(ps==')' && stack.peek()=='(')
                stack.push(ps);    
            else
                stack.pop();
        }
        
        if(stack.isEmpty())
            isValid = true;
        else
            isValid = false;
        
        return isValid;
    }
}