Digital Mysteries: Search Algorithms is a unique app for 11-14 year olds which allows pairs to work simultaneously on one iPad with a task designed to help students develop understanding of key algorithms that reflect computational thinking.

This mystery shows students that in programming, as well as in real life, there are multiple ways to solve a problem. They are given lots of snippets of information about some school pupils being asked to think of a good way to sort books for the new school library. In order to come up with an answer on which method is best, users move through a carefully devised three stage process – they must first read all the slips, then organise them into groups, then move to the final stage where they lay out the slips in a chain and use sticky tapes and notes to help make sense of everything.

Following this process, students can then go through the Reflection Stage. This allows them to play back what they have done, discuss their choices and share with others what they thought during the main task and whether, after reflection, they still think the same. This can be done alone, in their groups, with their teacher or as a whole class. A PDF report is also generated as a summary of the session, and is available to print or share.

There are three difficulty levels to choose from. Easy introduces three different approaches with their main advantages and disadvantages. Medium links these algorithms to computing science, and Hard gets students thinking about more challenging scenarios.

This app addresses two key topics in the computing curriculum: understanding algorithms with sorting and searching given as examples, and comparing the utility of alternative algorithms for the same problem. It shows in an un-intimidating way that when designing or choosing an algorithm to solve a problem, there’s usually compromises between the time taken to learn and implement an algorithm, and the time it takes to execute it. Faster algorithms, in many cases, are harder to understand and may take more time to implement, so the choice of the algorithm depends on whether speed is critical, whether it is frequently used or not, and the time available to implement the algorithm.

It is important that the students realize that there is not necessarily one right approach for all cases; what works best for the scenario given in the mystery is not necessarily the best when there are fewer or more books.

Suggestions for key learning goals when doing this mystery:

- Learn what algorithms are by using a simple formal definition supported by practical scenarios of three different algorithms to perform the same task

- Understand several key algorithms that reflect computational thinking (such as sorting, to speed up searching)

- Use logical reasoning to compare the utility of alternative algorithms for the same problem

How can I try other mysteries?

At the bottom of the app details tab, tap ‘Developer Apps’ to view our current range. There are apps for various subjects including computing, geography, history, mathematics, citizenship and Shakespeare plays Romeo and Juliet, A Midsummer Night’s Dream and Macbeth’s Influences.