Sorting in Scratch

Sorting is really important in Computer Science! There are lots of ways to do it: https://www.toptal.com/developers/sorting-algorithms

We are going to start with sorting pieces of paper and try to figure out how we can make a computer do it for us instead...

Step 1: Sorting pieces of paper

Find a partner and take a set of numbered squares

Lay the numbers out randomly in a row in front of one person.

One person is the "computer" and can switch two numbers at a time. However, they must follow a consistent pattern when pointing to two numbers, for example, going from left to right. They are essentially "blind" to what the numbers really are.

The other person is the "algorithm" and can only tell them "switch" or "don't switch". They can not give advice on where to point.

Step 2: Sorting in Scratch!

1. This is a link to a Scratch project called "Sorting Starter 10", open it in a new tab:
   • https://scratch.mit.edu/projects/125587510/#editor
   • Log into Scratch
   • Click the "remix" button to add the project to your files
2. The "a" key will create a random set of blocks
3. The "s" key will create a backwards-sorted set of blocks
4. The "d" is what you need to fill in! It calls "sort blocks" and you need to figure that out.
5. Inside the code, try out the "swap" function to see what it does. Try different numbers as arguments to see how it swaps positions.

There are some hints inside the project to get you started.

"Extra Credit":

Once you have completed sorting 10 items, use the same algorithm to sort 300 items in the project "Sorting Starter 300": https://scratch.mit.edu/projects/125493888/

Hint: you won't be able to just copy and paste this time. You will need a "loop" or a "repeat"

Can you sort 300 items in less than 0.5 seconds?