This was my first phone interview. The interviewer started by introducing himself, and within a minute, we began the technical interview. Only one question was asked. After listening to my various approaches, he kept adding more and more constraints.

If you are given an integer singly linked list, print it backwards.

Constraints:

• Do not manipulate the list (e.g., do not make it a doubly linked list, do not add or delete elements, do not change the memory location of any element).
• Time complexity: O(n) < time < O(n^2).
• Space complexity: O(1) < space < O(n).