In honor of CSEdWeek (Computer Science Education Week), I have a pledge to you all: I pledge to post a lesson plan or resource for every day of the week. I am a little behind, seeing as it’s already Tuesday, so I have some catching up to do.
Let’s start with Sunday, the first day of CSEdWeek. Since there’s no school on Sunday, I decided to turn my attention towards the usefulness of computational thinking around the home with my sock-sorting algorithm. Yes, you heard me right. Now, you can apply computational thinking to doing your laundry. But first, you might be wondering what I mean by computational thinking.
What is Computational Thinking?
Computational thinking builds on the power and limits of computing processes, whether they are executed by a human or by a machine. Computational methods and models give us the courage to solve problems and design systems that no one of us would be capable of tackling alone.
The beauty of computational thinking is that is helps us learn to use computers to solve problems or simply solve problems in any arena, such as dealing with the sock problem.
The Sock Problem
You’ve been there; I’ve been there too. Your laundry is piling high; your shirts are crushed under the weight of the three-plus loads you never bothered to fold; and now, your kids are looking for their underwear under their beds, in the laundry hamper, and anywhere but where they are supposed to be.
You head out to the laundry room, grab that pile of clothes and begin sorting. You start with the towels—they’re easy to find, easy to fold, and take up most of the bulk. Next, you find pants and shirts and go to work on them. Things are going well, in little to no time, your mountain of clothes is now more like the steppe of clothes.
You’re back is getting sore, but you plod on. You deal with t-shirts and underwear, and then, at the bottom, you see them: the socks. They lie in wait . They are the wiley clothes; in the many years you have folded laundry, you’ve never seemed to have completely folded them all. They are the smallest of the clothes, so even though they take up an eighth of the bulk of clothes, in number, they represent over half of the items in your laundry. If this weren’t bad enough, after dealing with the 30-some items of laundry, you’re still left with mis-matched socks and orphans. We’re they leftovers from a kid sleepover? Did one get lost at the last campout? Did they slip through your drier into another dimension…?
Few sober-minded laundry folders savor the thought of dealing with the socks. Socks are, after all, the dregs of laundry. Typically the last thing a person wants to do is go through this hodge podge of clothes: a sock jambalaya, as it were. Really, who in their right mind wants to go through the tedium of sifting through the 40+ socks to find their mates and return them to home base? What you need is a sock folding algorithm.
The solution takes on two phases: divide and conquer and sort and match.
Divide and Conquer
Phase one has two steps that each follow the classic, Divide and Conquer algorithm. It’s where you divide your targets in half (or thirds or quarters). By doing this, you are able to focus on no more than half of the possible outcomes at any given time. We’ll still have to deal with both halves in my sort, but this method helps you to not concern yourself with all the possiblities and focus on a manageable chunk.
With this in mind, the goal here is not to overthink.
Begin with a general sort by color: this is no time to think, this is time to quickly toss your socks into one of two (or three) piles:
- Multi-colored (this is optional, but often times necessary near the holidays)
- Feel free to add a stack for greys &/or browns (also optional)
Sort by Size: Take each of the three piles and apply one more general sort. Again, this is a quick divide and conquer sort without any thinking. The more you think, the longer and more cumbersome it becomes.
- Short Socks here you want just socks that go no higher than above the ankles
- Long Socks any sock longer than ankle length go in here
Apply a Sort to the Remaining Piles
At this point, you have 2-3 or so stacks of socks. It didn’t take long at all because you quickly divided them. Your job now is to sort each stack. There are all kinds of sorting methods, but there are two sorts worth mentioning: the bubble sort and the network sort. Some computer scientists will scoff at me for using the bubble sort, but remember, these are socks, not a table of database records.
The Bubble Sort: this is actually one of the most inefficient sorts as far as computer science goes, but in a short stack of maybe 10-20 socks, you probably won’t know the difference. Here’s how it goes. According to CSUnplugged.com
Bubble sort involves going through the list again and again, swapping any objects sideby-
side that are in the wrong order. The list is sorted when no swaps occur during a pass
through the list.
Technically, you aren’t actually sorting now. Instead you are matching socks with their mates, but the idea is the same, compare one sock to another, if it matches, fold them and pull them from the stack.
Network Sorting: in a network sort, you are applying multiple “threads” of sorting. You really need to watch the CS Unplugged Video on Sorting Networks or review the online lesson plan. Here’s how it works:
- Line all the socks from the remaining pile along the back of a couch
- Get your spouse and children (if you have them) to line up side by side starting on the left-hand side
- Each person takes a sock in front of them and compare to the person on your right.
Continue this process until all are sorted or you’re left with sad lonely socks
- If they match,
- If they don’t match,
- check to see which of the two is smaller and put the smaller sock on the left and the larger on the right
What do we do with the left-overs?
I knew you were going to ask. This depends on your attitude. If you notice that a particular sock never seems to have a match or has a hole in it, it’s time to send it to the cleaning rag pile. If that solution does suit you—maybe you’re more the creative type—you could make a sock monkey or finger/hand puppet.
I’m sorry that my solution doesn’t sound much like computational thinking, but according to the Exploring Computer Science (ExploringCS) Curriculum…
analysis of various solutions and algorithms will highlight problems that are not easily solved by computer and for which there are no known solutions. (p. 21)
Maybe the leftovers are a traditionally unsolvable problem by computer standards. If so, maybe it can become a Turing Test.