🟩 [백준] [Java] [Silver4] 10866_덱

문제

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

10866번: 덱

풀이

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.Buffer;
import java.util.*;

public class 덱 {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        StringBuilder sb = new StringBuilder();
        Deque<Integer> deque = new ArrayDeque<>();

        for(int i=0; i<n; i++){
            StringTokenizer st = new StringTokenizer(br.readLine());
            String s = st.nextToken();

            switch(s){
                case "push_front":
                    deque.addFirst(Integer.parseInt(st.nextToken()));
                    break;
                case "push_back":
                    deque.addLast(Integer.parseInt(st.nextToken()));
                    break;
                case "pop_front":
                    if(deque.isEmpty()) sb.append(-1).append("\n");
                    else sb.append(deque.pollFirst()).append("\n");
                    break;
                case "pop_back":
                    if(deque.isEmpty()) sb.append(-1).append("\n");
                    else sb.append(deque.pollLast()).append("\n");
                    break;
                case "size":
                    sb.append(deque.size()).append("\n");
                    break;
                case "empty" :
                    if(deque.isEmpty()) sb.append(1).append("\n");
                    else sb.append(0).append("\n");
                    break;
                case "front":
                    if(deque.isEmpty()) sb.append(-1).append("\n");
                    else sb.append(deque.peekFirst()).append("\n");
                    break;
                case "back":
                    if(deque.isEmpty()) sb.append(-1).append("\n");
                    else sb.append(deque.peekLast()).append("\n");
                    break;
            }
        }
        System.out.println(sb);

    }
}

자바의 Deque를 이용하여 풀었다. 덱이 비어있을 때를 주의하여 해결하면 된다.