[java 백준] 실버 4/ 10866번 덱

https://www.acmicpc.net/problem/10866

10866번: 덱

import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Deque;
import java.util.LinkedList;
import java.util.Scanner;
 
public class Main {
 
    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringBuilder sb = new StringBuilder();
        Deque<Integer> queue = new LinkedList<>();
        int num = sc.nextInt();
        int n = 0;
        int n2 = 0;
        for (int i = 0; i < num; i++) {
            String order = sc.next();
            if (order.equals("push_front")) {
                n = sc.nextInt();
 
                queue.addFirst(n);
            } else if (order.equals("push_back")) {
                n2 = sc.nextInt();
                queue.addLast(n2);
            }
 
            else if (order.equals("pop_front")) {
 
                if (queue.isEmpty()) {
                    sb.append(-1).append('\n');
                } else {
                    sb.append(queue.pollFirst()).append('\n');
                }
 
            } else if (order.equals("pop_back")) {
 
                if (queue.isEmpty()) {
                    sb.append(-1).append('\n');
                } else {
                    sb.append(queue.pollLast()).append('\n');
                }
 
            } else if (order.equals("front")) {
                if (queue.isEmpty()) {
                    sb.append(-1).append('\n');
                } else {
                    sb.append(queue.getFirst()).append('\n');
                }
 
            } else if (order.equals("back")) {
                if (queue.isEmpty()) {
                    sb.append(-1).append('\n');
                } else {
                    sb.append(queue.getLast()).append('\n');
                }
 
            } else if (order.equals("size")) {
                sb.append(queue.size()).append('\n');
            } else if (order.equals("empty")) {
                if (queue.isEmpty()) {
                    sb.append(1).append('\n');
                } else {
                    sb.append(0).append('\n');
                }
            }
 
        }
        bw.write(sb.toString());
        bw.close();
 
    }
 
}