Remove Linked List Elements

Remove Linked List Elements

What is this problem about?

The Remove Linked List Elements interview question asks you to delete all nodes from a singly linked list whose value equals a given target value val, and return the modified list's head. The target value may appear multiple times, including at the head of the list, making head-management an important aspect of the solution.

Why is this asked in interviews?

This problem is asked at Apple, Microsoft, Meta, Amazon, Oracle, and Google as a fundamental linked list manipulation exercise. It tests in-place node deletion, pointer management, and the use of a dummy node to simplify edge cases. It is often used as a stepping stone to harder problems like reversing sublists, removing the nth node from the end, and detecting cycles.

Algorithmic pattern used

The pattern is linked list traversal with a dummy (sentinel) head node. Create a dummy node with dummy.next = head. Use a curr pointer starting at dummy. While curr.next is not null: if curr.next.val == val, skip it by setting curr.next = curr.next.next. Otherwise, advance curr = curr.next. Return dummy.next.

Example explanation

List: 1 → 2 → 6 → 3 → 4 → 5 → 6, target = 6.

• dummy → 1 → 2 → 6 → 3 → 4 → 5 → 6
• curr=dummy. next=1 (≠6) → advance. curr=1.
• next=2 (≠6) → advance. curr=2.
• next=6 (=6) → curr.next = curr.next.next (=3). Now: dummy→1→2→3→4→5→6.
• curr=2. next=3 (≠6) → advance. curr=3. Then 4, then 5.
• curr=5. next=6 (=6) → curr.next = null.

Result: 1 → 2 → 3 → 4 → 5.

Common mistakes candidates make

• Trying to handle head deletion as a special case without a dummy node, leading to complicated conditional logic.
• Advancing curr even when a node is deleted, potentially skipping the next node.
• Not handling an empty list (head is null).
• Forgetting to handle multiple consecutive target nodes (e.g., 6 → 6 → 6).

Interview preparation tip

For the Remove Linked List Elements coding problem, the dummy-node pattern is the single most important technique to internalize. It converts head-deletion into just another middle-deletion, dramatically simplifying your code. Interviewers at Yahoo and Oracle often test this exact problem with the head being the target value — make sure your dummy-node approach handles it cleanly. The linked list and recursion interview pattern also works elegantly here as an alternative.