Question

The problem is that i need to write a recursive algorithm for reversing a singly linked list L, so that the ordering of the nodes becomes opposite.
it seems a bit abstract, but i don’t need code or anything and since the problem requests an algorithm, i am kind of stuck.
I don’t know were to begin, i mean i have had some simple things to do regarding linked lists, like add to the front and delete but, reversing (and especially recursive) seems like a wall.

Answer 1

Since you don’t need to provide specific code, I’d be doing your homework if I even gave you pseudo code, so I’ll just give you some hints 😉

The general approach would be to do

1. Cover the base case (if the given list is empty, return the empty list)
2. Recurse and reversing the tail
3. Append the head to the reversed tail.

To reverse 1 -> 2 -> 3 it would go like

  reverse(1 -> 2 -> 3)
= reverse(2 -> 3) -> 1
= reverse(3) -> 2 -> 1
= reverse() -> 3 -> 2 -> 1
= emptyList -> 3 -> 2 -> 1
= 3 -> 2 -> 1