--- title: Monkey class - Advent of Code Day 11 with Ruby slug: monkey-class-advent-of-code-day-11-with-ruby published_at: 2022-12-11 22:00:07 +0000 updated_at: 2026-03-04 20:15:11 +0000 summary: description: Monkey class - Advent of Code Day 11 with Ruby Challenge: https://adventofcode.com/2022/day/11 Solution: https://gist.github.com/cjavdev/8334e7dfef0a47076b90f1af8382d6f4 #ruby #adventofcode tags: [cjav_dev, web development tutorials, web development for beginners, vim, ruby, advent of code, advent of code 2022, advent of code 2022 day 11, advent of code with ruby, advent of code ruby, advent of code 2022 day 11 with ruby, classes, object oriented programming, shift, queue] views: 244 author: CJ Avilla url: https://www.cjav.dev/videos/monkey-class-advent-of-code-day-11-with-ruby youtube_url: https://www.youtube.com/watch?v=GbUmGhF-BGo youtube_id: GbUmGhF-BGo embed_url: https://www.youtube.com/embed/GbUmGhF-BGo thumbnail_url: https://i.ytimg.com/vi/GbUmGhF-BGo/hqdefault.jpg type: video --- # Monkey class - Advent of Code Day 11 with Ruby *Published: December 11, 2022* *Views: 244* ## Watch [Watch on YouTube](https://www.youtube.com/watch?v=GbUmGhF-BGo) [![Monkey class - Advent of Code Day 11 with Ruby](https://i.ytimg.com/vi/GbUmGhF-BGo/hqdefault.jpg)](https://www.youtube.com/watch?v=GbUmGhF-BGo) ## Description Monkey class - Advent of Code Day 11 with Ruby Challenge: https://adventofcode.com/2022/day/11 Solution: https://gist.github.com/cjavdev/8334e7dfef0a47076b90f1af8382d6f4 #ruby #adventofcode ## Transcript what's up welcome back in this episode you'll learn how to solve day 11 for the Advent of code in 2022 with Ruby this one's called monkey in the middle we're continuing to help elves to track down the star fruit and save Christmas for today's challenge we fell off the bridge we're floating down the river and monkeys have started to grab stuff out of our backpack and they're playing monkey in the middle just tossing our items to each other and they're trying to keep them away from us we need to figure out which monkeys we want to Target to make sure that we can get our items back that mean the most to us so there is a factor of how much you're worried about your stuff being ruined and this is the input so our input for today is going to be broken up like this where we have several different monkeys some of them have different items I kind of like to imagine the 79 is some airpods this 98 might be cell phone and then these lower items I don't know they they matter less to us because we're less worried about them so each monkey is going to start with some items and then each monkey has some operation here that they're going to use to figure out how worried we are that they're going to damage an item so this is kind of like the way that they figure out if an item matters to us is by applying the value of the item or the worry that we have for the item by some amount and then checking to see if the amount that we're worried is divisible by 23 then it'll throw it to one if it's not divisible by 23 it'll throw it to another monkey and we go through the same process and each monkey's operation is different each monkey has a different set of items each monkey has a different like way that they're going to test how worried we are these monkeys are gonna throw items to each other and they're also going to have some State and so the way that I want to model this is using classes so we'll start off by just parsing out this input so we'll start with a class called monkey and we're gonna have a class method here called parse that's just going to take in some monkey data and first we'll just say like data.read dot split on two newlines that'll make sure that we're breaking up by monkey and then we'll just pass in this whole chunk as some like monkey data dot each do monkey data and then we're going to say like monkey dot parse monkey data okay and that's not going to give us any output to start but we can say I don't know let's just say like monkey dot new and we'll also keep track of our list of monkeys here with a with a dictionary and we'll make another method here called like all and that'll just give us back our monkeys okay all right so let's see what we can get if we say print out monkey dot all after we've read in our monkeys and parse them now we need to say like at monkeys at some value is monkey dot new I think we're just going to use like the name of the monkey because down here each monkey well it's numbered right so monkey zero monkey one monkey two monkey three this sort of names the monkey so that we can throw to another monkey so monkey zero will receive a an item thrown from Monkey one so we want to be able to use this as an index into our list of monkeys but we also want to make sure that we're tracking that sort of as the name of the monkey so let's let's start to parse out some monkey data so we'll just say monkey data dot split on new line and that'll get us all of these different lines and there should be six that we get back zero one two three four five and maybe the bottom so or yeah I started with zero so let's just say n for name I for items o for operation t for test and then TR for true and F A for false and then we'll use that to parse out our name so the name is going to be n dot split on space or colon and let's see what we get back oh and then we want to use that as our name here so name and okay so now we have a dictionary of all the monkeys and they have a name but the name is a string so let's make sure that that is converted to an integer all right run this again all right so now we have zero pointing at a monkey one pointing at a monkey two it's so on and so forth now when we initialize a monkey we could give it a name but we definitely need to give it some items and so we'll start with items and to get the items we want to split this line unlike colon space and then we want everything after that to be split yeah so here we'll say items is going to be I dot split colon space dot last dot split on comma.map to integer let's see if that gives us some items here all right so we run this okay so now we have some items for our monkey we also are going to need to keep track of the operation that is going to be applied and here the operation is is actually like valid Ruby code right we could have a variable called new and a variable called old and some multiplication or we could just use like this value on the right hand side of the equals as our operation that we're going to apply so I think I want to split on the equals space for the operation so we're going to say operation is going to be o dot split on this and we want the whole string value we'll use eval today to like actually evaluate that code as if it was Ruby all right what else do we want here and then we also want the divisible by so the test is always going to be whether or not it's divisible by something so for our zero monkey it's 23 then 19 then 13 then 17. so we can just grab like our t or yeah we'll just call it test is going to be T dot split on Space Dot last.2i call this test okay test oops test test all right and then we need to know maybe like the success monkey and the failure monkey or something okay so we'll just say like success monkey failure monkey okay so we have our success monkey is gonna be TR Dot yeah in our failure monkey is going to be f a DOT split okay so now we should have a bunch of monkeys that are parsed into the appropriate thing we didn't actually take those in here so success monkey failure monkey and boom okay so for this first monkey we've got our operation that's going to be old times 19 we have a test value that we're going to divide by we have a success monkey we have a failure monkey so on and so forth okay so what we've done here is we've created a class method called parse and here we're using a in a class instance variable called monkeys and we're keying into this hash for the for the whole class the whole monkey's class right and we're going to keep track of all of our monkeys and then we have this helper method that gives us back the list of monkeys here right now we're just initializing with some data and at this point we're ready to start taking some action with our monkeys the monkeys are going to take turns looking at every single item in their list going through it inspecting it figuring out the worry level and then throwing it at the end of a turn the monkey will have nothing left in their own items and then once all of the monkeys have gone through their items they each monkey may or may not have received some as part of as part of that round and around is going to be when every single monkey goes through and inspects all their items so what we need to do is have some concept of inspect I'm going to call it INSP this is going to be when a monkey inspects its items so this is going to every time a monkey inspects an item it's going to say pull the item off of the stack so at items.shift so shift if you haven't seen it before is a way that you can modify an array so if we have a and it's like one two three four we can say a DOT shift and it's kind of like pop but instead of pulling the item off the end it pulls it off of the front this is the order in which we want to look at our items is from the front of the list so we're going to treat this as a cue first in first out okay so the first thing we do is we pull the item off of our list and then we need to apply our operation so that we can see what we get back so item is going to be like apply operation of item and here apply operation of the item if we look at the actual operations that we're given in our in our test example it's always going to use this word old and then some some operand and operator and so what I want to do is actually I'm just going to call apply operation I'm going to use old as the variable name and then here we can use eval so we're just going to eval at operation because again the operations are like old plus six or Old Times old or Old Times 19 and so if we have an argument here called old then when we evaluate the operation it's going to run like old plus six or old times six or something so this is this is a use of eval typically I would never use this you know like in a real scenario but this is kind of a fun use case for it okay so we're gonna apply the operation and then we are going to divide the worry level by three because the monkey gets bored with the item so we're gonna say item divided by three then we need to check if the item is divisible by the number by the test or then this is going to be like our two monkey is going to be apply test on the item so we need to make a new method apply test on some item and that is going to use our test so we're going to say something like if or like item if it's divisible by test then we want to return the success monkey otherwise we want to return the failure monkey so then that's going to give us where we're throwing the item and now we can reach into all monkeys and go to our two monkey and say like throw item item actually we can make yeah whatever or let's make the method catch item in fact let's call it like throw item to Monkey item and then we'll make a new method here called Throw item and it's going to take in the two or yeah the monkey in the item and then we'll reach into monkey dot all at Monkey and we'll say catch item and we're going to pass them an item and then we'll make a new method here called catch item and we need to add the item to that other monkey's list of items and in this case we are going to add it to the end this is one round of inspection so let's see if this actually works so let's grab monkey dot all at zero dot inspect and see what happens or then we'll just like P monkey dot all at zero foreign all the monkeys okay so after we run the first time so the monkey started with the monkey started with 79 Now it only has 98 so it looks like it actually did remove that and after this first round we should have tossed 500 to Monkey three so does monkey three now have okay so monkey three now has 500 in its list so I think that worked so now what we need to do is go through all of the monkeys and do a round So Def self dot round and so here we'll say like monkeys Dot each do monkeys.values that each do or yeah each and we need to inspect all we can so this is this inspect right here is just a single item so we'll just say like inspect all is a new method where we're going to say while items while there's any items we want to call inspect so this should go through every single monkey and call inspect all on it and then inspect all should go through all of those monkeys items and we should end up with monkeys that have stuff at a different in a different monkey's hand and we don't actually see anything after that so let's pee monkey dot all or we need to do like monkey dot round and then monkey dot all monkey is a fun fun class name all right so then what we want to do is we expect that after a single round monkey zero has 20 23 27 26 20 23 27 26. and monkey one has 2080 25 160 okay and then monkey one has this and then the other two monkeys don't have any items fantastic okay so round one was successful but we need to go 20 rounds so chasing all the monkeys at once is impossible we're gonna have to find the two most active monkeys so count the total number of times each monkey inspects items over 20 rounds so first thing we need to do is do these rounds 20 times so around and then we'll make round take in some numbers so this is going to take in some number n and then we'll say like n dot times do okay so that'll run 20 times or whatever number of times we need to run we also need to keep track of the number of times we're inspecting so here we'll just say like at inspection count plus equals one and we'll start off our inspection count in initialize at inspection count we'll start off at zero I'm going to move this initialize method up right under the class methods I'm trying to organize it so that I have like macros at the top and then we have our class methods and then we have our initialize method followed by all of the instance Methods at the bottom I like that sort of pattern and let's see what we get here okay so now we have these inspection counts and monkey zero should have inspected 101 and it did and monkey three inspected 105. so now what we need to do is figure out which two monkeys or the most active self.active monkeys notice that anytime that I'm working with a collection of monkeys so whether we're going over we're looking at all the monkeys or we're iterating over several monkeys to apply around or we're looking at the Active monkeys I'm creating class methods to operate on the whole collection and then otherwise we're operating on individual monkeys active monkeys here is going to be at monkeys.values Dot map inspection count dot reduce times so this is actually going to be inspection count dot sort dot take to dot inject well that's the monkey business right so let's get our active monkeys so inspection count right here when we're when we're mapping across a monkey and we're trying to call the inspection count method on the monkey right now it's going to fail because there's no method for that right because inspection count is an instance variable so if we try to call Monkey like P Dot monkey active monkeys down here that's gonna fail because it's gonna say inspection count is not a valid thing because we need to make a reader method for our inspection count instance variable so add our reader for inspection count all right and all right so now we have 7 and 95 those are the wrong ones so we want to sort and reverse oops okay now we have 105 and 101 and so then monkey business is going to be active monkeys inject multiplication so I I'm like pausing here because I don't think this is actually like I think we want to do this a different way I think we want to say monkeys.values.sort by inspection count and then we actually want to do it like in Reverse so like that really should give us our our monkey our active monkeys like in order right so this should give us our most active monkey and then our second most active monkey and then our third most active monkey and so on and then from active monkeys down here then I can say like that take two dot map inspection count dot inject multiplication and that should give us back our monkey business so if we come down here and say Monkey Business run it again now we get 10 605 which is the test answer and okay so we have it working for the test use cases so we need to grab our puzzle input so we're going to grab all of our monkeys here we're going to create a new file called input drop it in and we need to update our code here so that it reads from if our V Dot empty we're going to read from there otherwise we're going to read our data from file dot read arcv0 and then we're going to apply the same stuff so input okay so 110 220 is that my answer one hundred ten thousand two hundred twenty boom okay great so that's part one okay so in part two you're worried you might not get your items back so so worried in fact that your relief that a monkey inspection didn't damage an item no longer causes your worry level to be divided by three instead of 20 rounds now we need to go 10 000 rounds it's going to tell us here's how much each monkey has inspected after that many rounds and after ten thousand rounds we're going to still use the same sort of Monkey Business thing but now we want to we want to go 10 000 rounds so instead of 20 rounds we want to go 10 000. now as we run through this right if we give it our input it's going to take a second and this output is massive right so this is uh 32 billion something something something but the the difference is that we are no longer dividing by three after each item is inspected okay so if we come up here and we just say like oh let's just remove our division by three and rerun this then it's just going to hang because the numbers become so massive because if we're not dividing by three and the item like the worry about the item isn't ever kind of like getting cut down then the the values for those items becomes massive especially because one of our operations here is Old Times old so that's going to grow N squared right like the size of the value for n is going to grow N squared and that becomes just like impossible to manage so what we need to do is figure out what we're going to do instead of dividing by three we want to do is make sure that the math continues working out every time we apply an operation and then do this test it should continue working and so what I think makes the most sense is to use the greatest common divisor of our items and the greatest common divisor so that our tests all still work would be to take the product of all of our tests to figure out what we want to ultimately divide by and instead of dividing we're going to use the remainder okay so we need to have like some some greatest common divisor thing so deaf self dot relief okay so relief is going to be monkeys Dot values.map test so we want to get the tests for all the different monkeys so we need to add that as a reader and for now let's just try printing out our relief so we're going to comment this out and we'll say p.monkey dot relief okay all right so right now we're getting all the test values that's great now we need to get the the product of all of those so now we need to say map inject or just inject so that we multiply them all against each other and we're going to get some number so this is this is the number that we're gonna like modulo by and we can do that inside of our inspection step so we want to actually say like item mod equals monkey dot relief okay so that should give us something much better okay so now we need to run this 10 000 rounds and instead of just hanging forever it should finish okay so it did finish and we got this big number one nine it starts with okay boom that was the puzzle answer for part two we used a class today and we we did this because each monkey encapsulated some data and it also had some Behavior some methods that we wanted to use to interact with other monkeys we used Class methods for the collections and for this like Factory method for parsing sets of monkeys and then we added lots of different helpers on the class itself to interact with collections of monkeys and we finally like and we were able to implement this very the inspection algorithm pretty simply because we were able to break out the application of the operation the application of the test the application of like throwing an item to another monkey all into these other methods so this was pretty cool I think one other thing that might be interesting is to talk about how like we can make this method protected because we want to call catch item from another monkey and then we can make these private because we're calling them from our from inside of our inspect method and then we could even we could even I think move inspect down inside of our private methods and that that would give us some like actual like use the actual method privacy that's built into Ruby for our class all right I think we're gonna leave it at that thanks again so much for watching and we'll see you in the next one --- [Back to all videos](https://www.cjav.dev/videos) --- ## Hey Agent, thanks for visiting! 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