Java 10866 덱

 

풀이 :

고정된 크기의 int형 배열을 생성한 뒤 index를 가운데에서 설정하고 생성해주었습니다.

이전에 풀었던 스택 구현 문제와 기능만 더 구현하면 되는 문제라 쉽게 풀 수 있었던 문제였습니다.

 

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

public class Main {

    static class CustomDeque {
        private int[] deque;
        private int front;
        private int rear;
        private int size;

        public CustomDeque(){
            this.deque = new int[20001];
            this.front = 10000;
            this.rear = 10000;
            this.size = 0;
        }

        public void pushFront(int n){
            deque[front] = n;
            front--;
            size++;
        }

        public void pushRear(int n) {
            rear++;
            deque[rear] = n;
            size ++;
        }
        public int popFront(){
            if(size == 0){
                return -1;
            }
            int i = deque[front + 1];
            front ++;
            size --;
            return i;
        }
        public int popBack(){
            if(size == 0){
                return -1;
            }
            int i = deque[rear];
            rear--;
            size--;
            return i;
        }

        public int size(){
            return size;
        }

        public int empty(){
            if (size == 0) {
                return 1;
            } else {
                return 0;
            }
        }
        public int front(){
            if(size == 0){
                return -1;
            }
            return deque[front + 1];
        }
        public int back(){
            if(size == 0){
                return -1;
            }
            return deque[rear];
        }
    }

    public static void main(String[] args) throws IOException{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        CustomDeque deque = new CustomDeque();
        StringTokenizer st;
        StringBuilder sb = new StringBuilder();
        for(int i = 0 ; i < n; i++){
            st = new StringTokenizer(br.readLine());
            String str = st.nextToken();
            switch (str) {
                case "push_front":
                    int j = Integer.parseInt(st.nextToken());
                    deque.pushFront(j);
                    break;
                case "push_back":
                    int k = Integer.parseInt(st.nextToken());
                    deque.pushRear(k);
                    break;
                case "pop_front":
                    int i1 = deque.popFront();
                    sb.append(i1).append("\n");
                    break;
                case "pop_back":
                    int i2 = deque.popBack();
                    sb.append(i2).append("\n");
                    break;
                case "size":
                    int size = deque.size();
                    sb.append(size).append("\n");
                    break;
                case "empty":
                    int empty = deque.empty();
                    sb.append(empty).append("\n");
                    break;
                case "front":
                    int front = deque.front();
                    sb.append(front).append("\n");
                    break;
                case "back":
                    int back = deque.back();
                    sb.append(back).append("\n");
                    break;
                default:
                    break;
            }
        }
        System.out.println(sb);
    }
}