IB Computer Science HL · Year 2 · Lesson 22
Singly linked lists
Abstract data types separate what operations mean from how they are implemented, helping you choose structures by behaviour and trade-offs.
Paper 250 minutesB4.1.3
Use Next or the arrow keys.
Today’s targets
What you need to be able to do
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- Construct + applyAnd apply linked lists: singly, doubly and circular
B4.1.3
Paper 2 lensMatch the depth of every response to the command term. Previously learned content can move quickly, but retrieval must still be accurate.
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Retrieve
Rapid Recall Deck
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Say the answer aloud before flipping. Mark secure knowledge quickly and spend time on the gaps.
- What links does a node in a singly linked list store?: Its data and one link/reference to the next node.
- What is the purpose of the head reference in a singly linked list?: It identifies the first node and therefore the entry point for traversing the list.
- How is a singly linked list traversed?: Start at the head and repeatedly follow each node's next reference until the end is reached.
- What must change when inserting a node into a singly linked list?: The relevant next references must be updated so the new node is connected without losing the rest of the list.
- Why is searching a singly linked list usually sequential?: There is no direct indexed access, so nodes are followed from the head until the target is found or the list ends.
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B4.1.3 · Learn
Core knowledge and application
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B4.1.3Construct + apply
And apply linked lists: singly, doubly and circular
Abstract data types separate what operations mean from how they are implemented, helping you choose structures by behaviour and trade-offs.
Exam moveBuild the structure/solution and use it correctly in a new context.
Required detail 1The basic operations on a linked list, such as insertion, deletion, traversal, search
Assessment boundaryPaper 2
Explain it without notes
Construct + apply: And apply linked lists: singly, doubly and circular in the context of a system that needs efficient insertion, search and set membership.
- The basic operations on a linked list, such as insertion, deletion, traversal, search
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Worked example · B4.1.2 / B4.1.3
Singly linked list: structure and construction
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head→
Anext
→Bnext
→Cnull
class Node:
def __init__(self, data):
self.data = data
self.next = None
head = Node("A")
head.next = Node("B")
head.next.next = Node("C")class Node {
String data;
Node next;
Node(String data) { this.data = data; }
}
Node head = new Node("A");
head.next = new Node("B");
head.next.next = new Node("C");Insert after BCreate a new node D, set D.next to C, then set B.next to D. Explain why changing pointers in the wrong order can lose access to part of the list.
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Apply
Transfer to a new scenario
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ScenarioA system that needs efficient insertion, search and set membership needs a design or technical decision related to today’s topic. Explain what matters and why.
- The basic operations on a linked list, such as insertion, deletion, traversal, search
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Exam lens
Paper 2 practice
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Build the response before checking notesUse precise terminology and match the required depth.
- Construct + apply: And apply linked lists: singly, doubly and circular in the context of a system that needs efficient insertion, search and set membership.
Self-checkAnswer the exact command term. For explain, include mechanism/reason; for compare, pair criteria; for discuss/evaluate/justify, build supported reasoning and a conclusion.
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Homework
Finish the learning cycle
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IA — main task
Continue Criterion D development. Keep code readable, record meaningful implementation decisions, and maintain testing/evidence notes as you work.
Syllabus — short
Complete one targeted Paper 2/Paper 1 retrieval task from today’s lesson.
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End of Lesson 22.