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OCR H446 1.4.2 Data Structures exam transition

Part 14 of 14 · H446 1.4.2 · Data structures

The assessment piece for H446 1.4.2, worked independently and without checking answers along the way. An original community-transport scenario samples the whole specification point in one sitting, from structure selection and state tracing through to implementation reasoning and an evaluative recommendation, so it doubles as a readiness check before exam questions.

Students will:

  • recommend structures for a record, a fixed two-dimensional plan and an editable ordered list, with justification
  • describe stack and circular queue state changes including pointers and returned values
  • give safe linked-list pointer updates and a binary search tree comparison path with its insertion point
  • explain search and safe removal for two colliding keys in a chained hash table
  • reach and justify a recommendation between a queue and a stack under a new demand

Inside: 2 explanation cells, 1 multiple-choice question, 8 written answers and 1 trace table. 36 marks, about 70 to 85 minutes.

Series: H446 1.4.2 · Data structures, part 14 of 14.

Shared by Coding PathwayVerified teacher

  • 12 cells
  • About 75 minutes
  • CC BY-SA 4.0
  • Shared 31 Aug 2026
  • Updated 3 Sept 2026

Preview

The whole resource, exactly as a class sees it. Answers and marking are held back.

Data Structures exam transition

Complete this assessment independently and without checking answers as you go. Use the command words, supplied evidence and context carefully; correctness is held where the platform supports it.

This original community-transport scenario samples OCR H446 1.4.2. Work without notes. Auto-checkable feedback is withheld for teacher review; there is no teaching between questions.

Readiness

You should be able to select, create, traverse, add and remove using all named structures. For pointer questions, state the convention before updating state.

Scenario

A transport festival stores stops and routes, passenger requests, vehicle histories, stop records and fast lookup by stop ID. Some routes form a hierarchy; others form a directed network.

Written answer6 marks

Recommend structures for (a) one stop’s ID/name/access fields, (b) a fixed 10×20 seat plan, and (c) an editable ordered list of announcements. Justify each.

Give property and scenario link.

Students type their answer here.

Written answer5 marks

An array stack has topStack=3 as next free and values A,B,C. Describe push(D) followed by two pops, including pointer and returned values.

State each pointer update before the value stored or returned.

Students type their answer here.

Trace table4 marks

Trace the circular queue pointer updates.

Enter a value only when it changes. Follow pointers and output in execution order.

Use one row for each pass through the loop. Fill in a box only when that value changes on that row, and leave the rest blank.

ProgramPython
  1. queue = ["", "B", "C", ""]
  2. head = 1
  3. tail = 3
  4. count = 2
  5. for item in ["D", "E"]:
  6. queue[tail] = item
  7. tail = (tail + 1) % 4
  8. count = count + 1
  9. print(tail)
  10. print(count)
Trace table with 6 columns
RowqueueheadtailcountitemOutput
1
2
3
4
5
6
Written answer5 marks

A list is head=4; node 4 has (M,next=1); node 1 has (N,next=-1). Give logical order, then state safe pointer updates to insert X between M and N.

Use node indexes or names consistently.

Students type their answer here.

Written answer5 marks

Explain two differences between the directed route graph and a tree hierarchy. State one suitable representation for the graph.

Use precise vocabulary.

Students type their answer here.

Written answer4 marks

Insert 55 into the BST with root 50, right child 70 and 70’s left child 60. Give comparison path and final position. Then explain one effect of an unbalanced shape.

Use smaller-left/larger-right.

Students type their answer here.

Multiple choice1 mark

With hash key MOD 5, which bucket receives key 42?

  • A0
  • B2
  • C1
  • D4
Written answer4 marks

Keys 17 and 42 collide in bucket 2 using chaining. Explain search for 42 and safe removal of 17.

Preserve the other key.

Students type their answer here.

Written answer6 marks

Evaluate a queue versus stack for passenger-support requests where emergencies may occur. Reach a recommendation.

Compare both on common criteria and apply priority issue.

Students type their answer here.

Written answer

Which structure or operation should you revisit, and what evidence supports that choice?

This reflection is not assessed.

Students type their answer here.