Good Learning Co.
SavannahYear 8
← Computing
ComputingAlgorithms and programming28 min★★★ difficulty

Sorting and searching

Choosing the right algorithm can be the difference between a million steps and twenty.

Part of your national curriculum
  • Algorithms and programming: Understand several key algorithms, including those for sorting and searching, and use logical reasoning to compare their utility

Lesson overview

What you'll learn in this lesson

Understand several key algorithms, including those for sorting and searching, and use logical reasoning to compare their utility

Key learning points

  • • Linear versus binary search
  • • Bubble sort
  • • Comparing utility

This lesson at a glance

  • 28 minutes
  • 14 parts to scroll through
  • 3 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

severalalgorithmssortingsearchinglogical

Scroll down — the lesson carries on below

Part 1 of 14 · Discover7%
1

Watch & discover

Part 1 of 14

Watch first

Sorting and searching

An English teaching video on this topic from LearnFree. Watch it, then scroll down for the lesson.

In a nutshell

Understand several key algorithms, including those for sorting and searching, and use logical reasoning to compare their utility

2

Learning cycle

Part 2 of 14

Learning cycle 1 of 2

Part 1 · Linear versus binary search

A short piece of teaching, then a check to make sure it has landed.

3

Explore the idea

Part 3 of 14

Learn

Linear versus binary search

Linear search checks each item in turn and works on any list. Binary search repeatedly halves a sorted list, so a million items takes about twenty checks instead of a million.

4

Explore the idea

Part 4 of 14

Learn

Bubble sort

Compare neighbouring pairs and swap them if they are the wrong way round, repeating until a full pass makes no swaps. Simple to write, slow on long lists.

5

Quick check

Part 5 of 14

Quick check

Binary search requires the list to be…

6

Reset break

Part 6 of 14

Pause

That's sitting 1 of 2 done

Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.

Stop here for now
7

Quick check

Part 7 of 14

Quick check

Roughly how many checks does binary search need for a million items?

8

Learning cycle

Part 8 of 14

Learning cycle 2 of 2

Part 2 · Comparing utility

A short piece of teaching, then a check to make sure it has landed.

9

Explore the idea

Part 9 of 14

Learn

Comparing utility

The best algorithm depends on the situation. Sorting first is only worth it if you will search the list many times.

10

Quick check

Part 10 of 14

Quick check

Bubble sort finishes when…

11

Challenge round

Part 11 of 14

Game · Sort it

Which of these are true?

Drag each card into the right column. Tap a card first if dragging is fiddly.

True

Not true

12

Challenge round

Part 12 of 14

Game · Fill the gaps

Finish the sentences

Choose the word that belongs in each gap.

____ first is only worth it if you will search the list many times.

13

Mastery quiz

Part 13 of 14

Marked quiz

End of lesson quiz: Sorting and searching

3 questions, marked with the reasoning shown. No timer.

  1. 1. Binary search requires the list to be…

  2. 2. Roughly how many checks does binary search need for a million items?

  3. 3. Bubble sort finishes when…

14

Lesson round-up

Part 14 of 14

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 3 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Article

How a supermarket checkout knows the price

When a barcode is scanned, the checkout does not store the price itself. It sends the barcode number to a database and reads back a record: product name, price, whether it needs an age check. The record is the single place the price lives, so changing one row changes every till in the shop at once.

Problems come from bad data, not bad scanners. If two products share a barcode, or a price update reaches the shop overnight but the till holds an old copy in its cache, customers are charged the wrong amount. Shops check this with test transactions: scan a known item, expect a known price, record what actually happened.

Good systems also log every scan. If a customer complains, the log shows exactly which record was used and when.

Written for Good Learning Co.

Reading questions

  1. Write in your own words what the checkout sends and what it receives back.
  2. Explain one way bad data could cause a wrong price, and how logging helps find it.
  3. Design a test table with four tests for a new checkout, with expected and actual results.

  • Reading and notes

    Reading

    Read the lesson text again and note the key terms and how each one is used, in your own words — as you would for revision.

    Half a page of notes

  • Extended writing

    Writing

    Explain a real system that uses this idea — how it works, where it can go wrong, and how you would make it safer or better.

    250–350 words

  • Algorithm on paper

    Diagram

    Write your steps out as pseudocode or a flowchart before you type anything, then photograph it.

    1 flowchart or 10 lines

  • Code write-up

    Writing

    Copy your code in, then explain underneath what each part does and what you had to fix.

    Code + 5 sentences

  • Test table

    Working out

    Make a test table: what you tried, what you expected, what actually happened.

    4–6 tests

Saved as you type.

Part 1 of 14 · Watch & discover

How this is going

  • Not looked at yet

    Understand several key algorithms, including those for sorting and searching, and use logical reasoning to compare their utility

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