You move a few pointers down the list and rewire the next pointers in place.

Earn the full sheet below.

When to use it

• You need to reverse, reorder, or remove nodes without extra space for a new list.
• The problem talks about next pointers, not indices, so array tricks don't apply.
• A 'convert to a list' solution works but costs O(n) space; this pattern uses fixed pointers instead.
• Locating a node relative to another (nth from the end, the middle) often pairs this with Two Pointers.

What's on the sheet

The guard rails never move. Step 3 does each problem's rewiring.

1. Define the node. A node only knows its value and what comes next.
2. Guard the edges. An empty or single-node list has nothing left to do.
3. Walk and Rewire. Each problem rewires differently; the walk is fixed.
4. Return. prev, not curr, is the new head.

Watch out

• Save curr.next into temp before overwriting curr.next = prev, or you'll lose the rest of the list.
• Removing at the head needs a dummy node. Remove Nth Node From End of List does this, and its fast pointer walks n + 1 steps ahead before both move together.

How to earn it

Solve half of the Linked List Manipulation problems and the sheet is yours. A free account works fine, and everyone earns their sheets the same way.

Want to see a finished sheet first? Preview the Two Pointers sample.

Every pattern has a sheet. See the full set.