Reverse Linked List Solution

You now understand both approaches. The iterative three-pointer technique is more space-efficient. The recursive approach is cleaner to write but uses $O(n)$ stack space.

For interviews, know both. Start with iterative unless the problem particularly asks for recursion.

Common bugs:

• Forgetting to save next before overwriting current.next
• Returning current instead of prev (current is null at the end)
• Not handling empty list or single-node list

Test your solution on: empty list, single node, two nodes, longer lists. Time: $O(n)$. Space: $O(1)$.