LESSON 14 · PATTERN GUIDE

Linked List Manipulation

Rewire node references carefully to reverse, merge, split, or transform lists in place.

FIRST, LEARN THE PATTERNUnlike arrays, linked lists are changed by updating next references. Keep references to nodes you still need before overwriting links.

The task asks to reverse part or all of a list, merge lists, swap nodes, or deep-copy nodes with extra references.

How to approach it

Use a dummy head for operations near the front; track previous, current, and next explicitly while changing links.

Watch out for

Losing the next pointer can disconnect the remaining list. Check head changes, null endings, and one-node cases.

A CLOSER EXPLANATION

A linked list stores order through references rather than neighboring memory positions. Before changing a link, save any node needed to continue the traversal. A dummy node gives the head the same handling as every other position and simplifies insertions or removals near the front.

NOW YOU TRY

Practice question

Reverse the linked list 1 → 2 → 3 → 4. What is the resulting order?

EXAMPLEhead = 1 → 2 → 3 → 4 → nullGive your answer before revealing the explanation.

Show a hint

For each node, save its next node before pointing it backward.

Show an answer

4 → 3 → 2 → 1 → null

CONNECT IT TO REAL LIFE

Linked List Manipulation at work

A playlist is A → B → C → D. You want to move D to the beginning without copying the tracks. Which links need to change?

Show one possible approach

Make the current tail D point to A, then make the old tail the new head and terminate the old predecessor C. Keep references to D and C before rewiring.

Practice next

Use these problem IDs to find additional practice for this pattern:

2123242592138