ITPEC FE Subject B October 2025 Question 10

The procedure insertAfter(targetData, newData) traverses a singly linked list starting from head, finds the node whose data matches targetData, and inserts a new node with newData immediately after it.

• •Blank A — loop condition: The traversal must continue while x is a valid node. The end of the list is signaled by x being undefined, so the condition is not undefined.

- Blank B — linking the new node: When inserting node y after node x, the standard two-step pointer update is:
1. y.next ← x.next — the new node takes over the link to whatever followed x
2. x.next ← y — x now points to the new node

If y.next were set to anything else (e.g., head, x, or x.next.next), the list would lose nodes or create incorrect links.

Why not others:
- a) B = head would point the new node back to the start, breaking the list
- b) B = x would create a circular reference between x and y
- c) B = x.data is a string, not a node reference — type mismatch
- e) B = x.next.next would skip a node, losing it from the list
- f–j) A = undefined would mean the loop runs while x IS undefined, which is the opposite of what we need — the loop body would never execute

Key rule: When inserting into a linked list, always save the "next" pointer of the current node before overwriting it — otherwise you lose the rest of the list.

AI-generated — may contain errors