Answer Happy

Operations on deque.
Description
You are given an empty deque. There are some incomplete methods
which execute on the deque, you should complete those methods to
get the required changes in the deque.

Note 1: Go through the comments in the program below.
Note 2: If you are asked to delete from the empty deque then print
“Not possible”
Note 3: The Deque given to you is named as "deque"

Sample Input:
10
1 5 1 4 1 2 1 1 1 3 3 4 5 2 6 6

Expected Output:
4
1
[6, 4, 2, 1]

Explanation:
Input:- The first line of input (here- 10)
is n. The next line contains
space-separated inputs. The inputs majorly contain values from 1 to
6. If the input is 1, the code takes the next value to be the
integer to input at the end of deque (here- 5 is next input to 1,
so the value is inserted into the deque at the end). Similarly is
for input 2, the code takes the next value to be the integer to
input at the head of the deque (here- 6 is next input to 2, so the
value is inserted into the deque at the head). For inputs 3, 4, 5,
6, the code works normally. If the input is 3, the value at the end
of the deque is deleted. Similarly, if the input is 4, the value at
the head of the deque is deleted. For input 5, the value at the
head of the deque is printed. For input 6, the value at the end of
the deque is printed.

Output:- The first line is the output of
input 5, that is 4 which is the value at the head of the deque (5,
4,2,1,3 are inserted at the end of the deque, then by input 3 and 4
the values 5 and 3 are deleted). The next line is the output of
last input 6 that is 1 which is the value at the tail of the deque
(after inputs 3 and 4, 2 the input which inserts the value 6 at the
head of the deque). The last line is the elements left in the
deque.
import java.util.*;
class Source {

public static Deque<Integer> deque = new
LinkedList<Integer>();
public static void add_atend(int data) {
//write the code to add 'data' at the
end of the deque.
}
public static void add_athead(int data) {
//write the code to add 'data' to the
front of the deque.
}
public static void delete_atend() {
//write code to delete an element at
the end of the deque
}
public static void delete_athead() {
//write code to delete an element in
the front of the deque.
}
public static int return_head() {
//write code to return the head of the
deque.
}
public static int return_tail() {
//write code to return tail of the
deque.
}
public static void main(String arg[]) {
Scanner in = new
Scanner(System.in);
int n = in.nextInt();
int value;
for (int j = 0; j < n; j++) {
value =
in.nextInt();
switch (value) {
case
1:

add_atend(in.nextInt());

break;
case
2:

add_athead(in.nextInt());

break;
case
3:

delete_atend();

break;
case
4:

delete_athead();

break;
case
5:

System.out.println(return_head());

break;
case
6:

System.out.println(return_tail());

break;
}
}
System.out.println(deque);
}
}