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: Time Limit Exceeded)

import java.io.IOException;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Scanner;
class Main{
	public static void main(String[] args)throws NumberFormatException, IOException{
//		System.out.println(" ");
		Deque<Integer> list = new ArrayDeque<Integer>();
		Scanner scan = new Scanner(System.in);
		int decAmount = scan.nextInt();
		int totalTime = 0;
		int[] number = new int[decAmount];	
		int check =0;
		String[] decree = new String[decAmount];
		

		for(int i=0; i<decAmount; i++){
			decree[i] = scan.next();
			if(decree[i].equals("insert") || decree[i].equals("delete")){
				number[i] = scan.nextInt();
			}
			///??????????????????
			if(decree[i].equals("insert")){
				list.addFirst(number[i]);
			}
			if(decree[i].equals("delete")){
				
//				check = list.indexOf(number[i]);
//				System.out.println(check);
//				if(check != -1){
					list.removeFirstOccurrence(number[i]);
//				}
			}
			if(decree[i].equals("deleteFirst")){
				list.removeFirst();
			}
			if(decree[i].equals("deleteLast")){
				list.removeLast();
			}
		}
		int times= list.size();
		for(int i=0;i<times;i++){
			System.out.print(list.poll());
			if(i == times-1){
				System.out.println("");
			}
			else{
				System.out.print(" ");
			}
		}
	}
}