[BOJ]백준 18258번:큐2(JAVA)

문제

풀이

코드

package baekjoon.solution;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Deque;
import java.util.LinkedList;
import java.util.Queue;
import java.util.StringTokenizer;

public class Baekjoon18258 {

        static int N;
        static Deque<Integer> q = new LinkedList<>();
        static StringBuilder sb = new StringBuilder();

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

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        N = Integer.parseInt(br.readLine());

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

            if(st.hasMoreTokens())
                push(Integer.parseInt(st.nextToken()));
            else if(str.equals("pop")){
                sb.append(pop()).append('\n');
            }else if(str.equals("size")){
                sb.append(size()).append('\n');
            }else if(str.equals("empty")){
                sb.append(empty()).append('\n');
            }else if(str.equals("front")){
                sb.append(front()).append('\n');
            } else if (str.equals("back")) {
                sb.append(back()).append('\n');
            }
        }


        System.out.println(sb);


    }

    public static void push(int i){
        q.add(i);
    }
    public static int pop(){
        if(q.isEmpty())
            return -1;

        return q.pop();
    }
    public static int size(){
        if(q.isEmpty())
            return 0;
        return q.size();
    }
    public static int empty(){
        if(q.isEmpty())
            return 1;
        return 0;
    }
    public static int front(){
        if(q.isEmpty())
            return -1;
        return q.getFirst();
    }
    public static int back(){
        if(q.isEmpty())
            return -1;
        return q.getLast();
    }


}