Write a function that takes the first Node in a linked list as argument and (destructively...

Write a function that takes the first Node in a linked list as argument and (destructively) reverses the list, returning the first Node in the result.

Iterative solution : To accomplish this task, we maintain references to three consecutive nodes in the linked list, reverse, first, and second. At each iteration, we extract the node first from the original linked list and insert it at the beginning of the reversed list. We maintain the invariant that first is the first node of what’s left of the original list, second is the second node of what’s left of the original list, and reverse is the first node of the resulting reversed list.

public Node reverse(Node x){Node first = x;Node reverse = null;while (first != null){Node second = first.next;first.next = reverse; reverse = first; first = second;}return reverse;}

When writing code involving linked lists, we must always be careful to properly handle the exceptional cases (when the linked list is empty, when the list has only one or two nodes) and the boundary cases (dealing with the first or last items). This is usually much trickier than handling the normal cases.

Recursive solution : Assuming the linked list has N nodes, we recursively reverse the last N- 1 nodes, and then carefully append the first node to the end.

public Node reverse(Node first){if (first == null) return null;if (first.next == null) return first;Node second = first.next;Node rest = reverse(second);second.next = first; first.next = null;return rest;}