Problem:
Doubly Linked List

Your task is to implement a double linked list.

Write a program which performs the following operations:

insert x: insert an element with key x into the front of the list.

delete x: delete the first element which has the key of x from the list. If there is not such element, you need not do anything.

deleteFirst: delete the first element from the list.

deleteLast: delete the last element from the list.

Input

The input is given in the following format:

n

command1

command2

...

commandn

In the first line, the number of operations n is given. In the following n lines, the above mentioned operations are given in the following format:

insert x

delete x

deleteFirst

deleteLast

Output

Print all the element (key) in the list after the given operations. Two consequtive keys should be separated by a single space.

Constraints

The number of operations ≤ 2,000,000

The number of delete operations ≤ 20

0 ≤ value of a key ≤ 109

The number of elements in the list does not exceed 106

For a delete, deleteFirst or deleteLast operation, there is at least one element in the list.

Sample Input 1

7
insert 5
insert 2
insert 3
insert 1
delete 3
insert 6
delete 5

Sample Output 1

6 1 2

Sample Input 2

9
insert 5
insert 2
insert 3
insert 1
delete 3
insert 6
delete 5
deleteFirst
deleteLast

Sample Output 2

1

Solution in JAVA (judge verdict: Wrong Answer)


import java.util.LinkedList;
import java.util.Scanner;

public class Main {
    static LinkedList<Integer> list  =new LinkedList<>();
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.nextLine());

        for(int i=0;i<n;i++){
            String[] sp = sc.nextLine().trim().split(" ");
            if (sp[0].equals("insert")){
                list.addFirst(Integer.parseInt(sp[1]));
            } else if (sp[0].equals("delete")){
                Integer m = Integer.parseInt(sp[1]);
                list.remove(m);
            } else if (sp[0].equals("deleteFirst")){
                list.removeFirst();
            }else if (sp[0].equals("deleteLast")){
                list.removeLast();
            }
        }

        for (Integer i=0;i<list.size()-1;i++){
            System.out.print(list.get(i)+" ");
        }
        System.out.println(list.get(0));
    }
}