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OCR H446 2.3.1 Algorithms consolidation

Part 15 of 16 · H446 2.3.1 · Algorithms

Everything in H446 2.3.1 meets here in one interleaved worksheet: representation, growth, searches, sorts, stacks, queues, linked lists, traversals and pathfinding, with no new content introduced. It is designed for the point in the course where students can each do the parts but choose the wrong method when the topic label is removed.

Students will:

  • correct a cluster of common misstatements about growth and running time
  • sort the same list twice by different methods and give a case-sensitive point for each
  • trace a stack-like process and contrast it with circular queue and linked-list updates
  • set out traversal orders with their controlling structures and the effect of graph cycles
  • plan and justify algorithms for a four-part route planner with preconditions and tests

Inside: 4 explanation cells, 1 multiple-choice question, 1 fill-in-the-blanks cell, 6 written answers and 1 trace table. 57 marks, about 60 to 80 minutes.

Series: H446 2.3.1 · Algorithms, part 15 of 16.

Shared by Coding PathwayVerified teacher

  • 13 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.

Algorithms consolidation

Complete the sections in order, beginning with retrieval and method selection before applying the ideas in integrated contexts. No new required knowledge is introduced.

This interleaved worksheet introduces no new content. Diagnose the representation, precondition, invariant, resource cost and boundary case before calculating.

Retrieval route

  1. Name the algorithm and required data state. 2. Show intermediate state. 3. State the dominant operation. 4. Check empty, smallest/largest, absent and duplicate cases.
Multiple choice1 mark

A sorted catalogue is searched repeatedly. Which pair is most defensible?

  • ALinear search, O(2ⁿ)
  • BBubble sort, O(1)
  • CBinary search, O(log n) worst/typical
  • DDFS post-order, O(n²)
Written answer6 marks

Correct and explain: 'n² is exponential; logarithmic work never increases; O(n) means exactly n milliseconds.'

Use input growth, not hardware time.

Students type their answer here.

Written answer10 marks

Sort [7,2,5,1] once with insertion sort and once with final-pivot quick sort. Show partition/pivot states and state one case-sensitive performance point for each.

Keep conventions visible.

Students type their answer here.

Trace table5 marks

Trace a stack-like process.

Enter a value only when it changes. Record output in 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. data = ['A','B','C']
  2. top = 2
  3. while top >= 0:
  4. print(data[top])
  5. top = top - 1
Trace table with 4 columns
Rowdatatoptop >= 0Output
1
2
3
4
5
6
7
Written answer7 marks

Explain the trace order, then contrast the state changes needed for a circular queue and a linked-list insertion.

Use LIFO, FIFO pointers and safe link order.

Students type their answer here.

Written answer7 marks

For the AL12 tree, give post-order DFS and BFS, name the controlling structure for each, and explain how graph cycles change the algorithm.

Include visited state.

Students type their answer here.

Written answer7 marks

Explain the different next-node choices made by Dijkstra and A*. Include one correctness condition for each and what happens when h=0.

Name the candidate set and compare Dijkstra's cumulative g with A star's f=g+h before stating each condition.

Students type their answer here.

Independent mixed design

A route planner must search place names, rank cached results, traverse category trees and find weighted routes. Select algorithms, identify preconditions, compare growth and propose boundary tests.

Written answer14 marks

Produce a justified algorithm plan covering all four needs and at least six tests.

Use scenario-linked criteria rather than a list of names.

Students type their answer here.

Final closed-book checkpoint

Complete each sentence from memory. There is no answer bank and correctness is held for teacher review.

Fill in the blanks5 marks
Repeated halving of sorted data identifies completion 1. Growing an ordered left partition identifies completion 2. Level-by-level tree processing identifies completion 3. Selecting the smallest tentative cumulative distance identifies completion 4. Selecting by known plus estimated cost identifies completion 5.

Review your understanding

Before submitting, check that you can explain the central distinction in your own words, expose the intermediate state that supports your answer and apply the method in an unfamiliar context.