BOJ 1406번 에디터

package BOJ;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Stack;

/**
 * BOJ 1406
 * stack 이용하지 않으면 B,P 연산 시간복잡도 O(n)
 * https://www.acmicpc.net/problem/1406
 */
public class Editor_1406 {

    private static Stack<Character> left = new Stack<>();
    private static Stack<Character> right = new Stack<>();

    private static char[] input;

    public static void main(String[] args) throws IOException {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        input = br.readLine().toCharArray();
        int cnt = Integer.parseInt(br.readLine());

        for (int i = 0; i < input.length; i++) {
            left.push(input[i]);
        }
        
        while(cnt-- > 0){
            String[] commandAndElement = br.readLine().split("\\s");
            doCommand(commandAndElement);
        }

        print();

    }

    private static void print() {
        StringBuilder sb = new StringBuilder();

        while(!left.isEmpty()){
            right.push(left.pop());
        }

        while(!right.isEmpty()){
            sb.append(right.pop());
        }

        System.out.println(sb.toString());
    }

    private static void doCommand(String[] commandAndElement){
        String command = commandAndElement[0];

        switch (command){
            case "L":
                if(!left.isEmpty()){
                    right.push(left.pop());
                }

                break;
            case "D":
                if(!right.isEmpty()){
                    left.push(right.pop());
                }
                break;
            case "B":
                if(!left.isEmpty())
                    left.pop();
                break;
            case "P":
                String element = commandAndElement[1];
                left.push(element.toCharArray()[0]);
                break;
        }
    }



}