How to Reverse a Linked List

A linked list is a chain of nodes where each node holds a value and a pointer to the next node. The list has a HEAD pointer that tells you where the list begins. The last node points to NULL, marking the end.

You cannot naively flip a pointer because you will lose access to the rest of the list. Initialize three pointers: PREV starts as NULL, CURR starts at HEAD, and NEXT starts as NULL.

Before making any changes, set NEXT equal to CURR.next. This ensures that after you break the current link, you still know how to advance to the remaining unreversed nodes.

Set CURR.next equal to PREV. This is the actual reversal step. The current node now points backwards to the previous node (or NULL if it is the first node being processed).

Update PREV to equal CURR, and update CURR to equal NEXT. This slides your entire working window one node forward.

Place the previous three steps inside a while loop that continues as long as CURR is not NULL.

When the loop finishes, CURR is NULL and PREV is pointing at the final node. Set HEAD equal to PREV. You have successfully reversed the list.