Find Pairs in a Doubly-Linked List

A sorted doubly-linked list of distinct positive integers is provided, along with an integer 'X'. Your task is to identify and print all unique pairs from the list whose sum equals 'X'.

Example:

Input:

10 20 35 50 75 -1
55

Output:

20 35

Constraints:

• 1 <= N <= 5*105
• -2*109 <= X <= 2*109
• -109 <= data <= 109 and data != -1

Input:

The first line contains elements of the doubly linked list, separated by spaces and terminated by -1 (which is not an element of the list).
The second line contains the integer 'X'.

Output:

For each unique pair where the sum is equal to 'X', print the pair in such a way that the first element is less than the second. Each pair should appear on a separate line, and the order of pairs does not matter.

Note:

No need to handle printing within the function. Simply implement the logic to return the answer.

Follow-Up:

Attempt to solve the problem with linear time complexity without utilizing additional data structures.