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 C (judge verdict: Accepted)

#include<stdio.h>
 
int main(){
  int i, j, a, num; 
  int y=0;
  int l, h, key;
  
  scanf("%d", &a);
  
  int list[a];
  char input[12];

  for(i=0;i<a;i++){
    scanf("%s %d",input,&num);
    
    if(input[0]=='i'){
      list[i]=num;
    }
    
    else if(input[6]=='F'){
      i-=2;a-=2;
    }
    
    else if(input[6]=='L'){
      i--;a--;y++;
    }
    
    else{
      i--;a--;l=0;
      for(j=i;j>=0;j--){
	if(l>0) break;
	if(num==list[j]){
	  key=0;
	  h=i-j;
	  l++;
	  
	  while(h!=key++){
	    list[j+key-1]=list[j+1+key-1];
	  }
	  i--;a--;
        }  
      }
    }
  }
  
  for(i=0;i<a-y;i++){
    if(i==a-y-1) printf("%d\n",list[a-1-i]);
    else printf("%d ",list[a-1-i]);
  }
  return 0;
}