--- title: Ranges and Sets overlaps, subsets, and intersection - Advent of Code 2022 Day 4 in Ruby slug: ranges-and-sets-overlaps-subsets-and-intersection-advent-of-code-2022-day-4-in-ruby published_at: 2022-12-04 22:45:01 +0000 updated_at: 2026-03-04 20:12:58 +0000 summary: description: Ranges and Sets overlaps, subsets, and intersection - Advent of Code Day 4 in Ruby. Challenge: https://adventofcode.com/2022/day/4 Solution: https://gist.github.com/cjavdev/2637d3d898554e8b82a834c25cc80339 #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 4, day 4, advent of code in ruby, advent of code ruby solutions, ruby solution, ruby tutorial, ruby tutorial for advent of code, advent of code day 4, ruby set, ruby range, overlaps, intersections, intersect?] views: 246 author: CJ Avilla url: https://www.cjav.dev/videos/ranges-and-sets-overlaps-subsets-and-intersection-advent-of-code-2022-day-4-in-ruby youtube_url: https://www.youtube.com/watch?v=zpuKrQUKty8 youtube_id: zpuKrQUKty8 embed_url: https://www.youtube.com/embed/zpuKrQUKty8 thumbnail_url: https://i.ytimg.com/vi/zpuKrQUKty8/hqdefault.jpg type: video --- # Ranges and Sets overlaps, subsets, and intersection - Advent of Code 2022 Day 4 in Ruby *Published: December 04, 2022* *Views: 246* ## Watch [Watch on YouTube](https://www.youtube.com/watch?v=zpuKrQUKty8) [![Ranges and Sets overlaps, subsets, and intersection - Advent of Code 2022 Day 4 in Ruby](https://i.ytimg.com/vi/zpuKrQUKty8/hqdefault.jpg)](https://www.youtube.com/watch?v=zpuKrQUKty8) ## Description Ranges and Sets overlaps, subsets, and intersection - Advent of Code Day 4 in Ruby. Challenge: https://adventofcode.com/2022/day/4 Solution: https://gist.github.com/cjavdev/2637d3d898554e8b82a834c25cc80339 #ruby #adventofcode ## Transcript what's up welcome back in this episode you're going to see how to solve day four for the Advent of code in 2022 with Ruby we're gonna talk about the range class the set class so there's a couple fun little Ruby nuggets in here the project for today is that we have to to handle some Camp cleanup elves are assigned different sectors and we're given a list of assignments where someone is supposed to clean section like two to four and then someone else is supposed to clean section two to or six to eight and we need to find which assignments have overlaps in the puzzles So within this first example two to four this this little visualization down here is actually the best so two to four and six to eight they don't overlap at all at the end our output for this puzzle is going to be the number of assignment pairs where there are overlaps so this one doesn't have an overlap this one doesn't have an overlap this one overlaps just on the seven and this one overlaps the entire thing so the top set covers come completely this bottom set so we would say like this bottom set is a subset of this top set or this top sort of like assignment of sectors and then this six is also fully included in four five six and so what we are trying to do for part one is to find the pairs where one of the assignments fully contains the other assignment so in this case three four five six seven is fully contained inside two three four five six seven eight and then also this six is fully contained within four five six those are the only two sort of assignment pairs where there's full containment the rest of these there's not so though that's like what we're trying to figure out let's let's just jump in and get started okay so we're going to make day four and in here what we're gonna do is we're gonna have our same little end at the bottom and we're gonna drop in our sample input and a lot of this is going to be string manipulation so we need to figure out how to get like this 2 4 and 6 8 to represent the assignments for two different elves and then we also need to convert them to integers and do a few different things so let's say that like data is going to be data.readlines and then we'll say results are data and we're going to map over that and Chomp that will give us just without the new line and then let's also map and we'll split but instead of splitting on the empty space we're going to spit split on the comma okay and let's just see what that gives us to start with okay so this again this is this first section here is just calling Chomp on each of the lines so that we remove the new line and then this here is going to split each line on comma and so we should get an array of arrays where we have kind of like 2-4 and 6-8 in each of the arrays so let's do that so we're going to say Ruby day four okay so now we have an array of arrays where each element is an array of the string two to four and six to eight so what I want to do now is split these further so that we remove the dash and then we have just 2 4 6 and 8. so what we can do is inside of this same the same split here now you'll notice too that I didn't use single quotes that would have worked just the same and we would get exactly the same result but I started off with using these slashes because this is how we can define a regular expression and what I want is I want to split on either the comma or the dash and that'll give us these arrays where the pairs are combined inside of the array but what's nice about that is then we can like pretty easily map over that and convert all of those into integers rather than strings let's see this the integer values fantastic okay now what we want to do is combine each of the pairs in the assignments so that we can see the range from 2 to 4 and the range from six to eight so now what we want to do is just say dot map each slice so line dot each slice of 2.2a so that should give us now like a pretty nested situation here okay so now we have an array of arrays of arrays or of like tuples maybe you want to say where we have two to four and six to eight so now these are in a format where we can take this two to four and make it a ruby range so a range is there's a range class we can say dot new and if we give it like 2 to 4 then that will give us this this range and you may have seen it in this like dot dot notation where we have a is the letters from A to Z and so now we can say a DOT member is is there a member here with the letter T and that will tell you like okay yes this thing is inside of the range of a so by creating a range from two to four this range two we can say dot two a and that'll give us the array that kind of explodes out the range from two to four so what's really convenient about working with ranges is that we can convert them also to sets so if we say require set if we require the set class and then we say like r.2 set this is going to convert it into yet another data structure so we have a couple different data structures here we're working with a range data structure that gives us like a minimum and a maximum and then you can ex explode that to have all the values in between and we're also going to work with a set which is a set of unique values the reason we want to use set is because there's some there's methods on set that will allow us to check if something is a subset or a superset and that'll be really handy so for instance if we wanted to say we'll say like R2 this is going to be a new range and we'll say that this new range is going to go from 1 to 6. so R2 is much longer than R so now we could say something like r2.2 set dot subset of r and that also needs to be arranged so R2 is not a subset of R but oops R is a subset of R2 so that kind of gives us the ability to like check if something is a subset or of another range so what we want to do now is we're going to map over this again and this time what we want to do is convert each of the pairs into a range and then convert that range into a set that doesn't actually work so say map okay so now we're still getting each line right and then each line is going to compa have two arrays okay so then each of those arrays are going to be converted into these sort of ranges where we're going to have some Like A and B so we'll have a and b and then we can say range dot Nu of A and B and let's just see what we get here and if that is going to map up to our expectation okay so now we have the ranges in their sort of like range notation of two to four six to eight three to two or two to three four to five etc etc so now that they're in this like range format what we can do is convert them to sets if we wanted to so we could also just as easily come up here and say range new DOT two set now anytime we work with sets we actually have to require the set gem because it's not part of Ruby by default so we have to require the same thing with Json or whatever okay so now we have now each of our groups here or our assignments are combinations of sets they're like tuples of sets so in the first assignment we have on the left we have a set on the right we have a set and what we want to do is we want to count up if the sets overlap right so now we're at the point where we actually want to reduce our list of sets down into some count so what we want to do now instead of map is called reduce and we're actually going to use our accumulator is going to be a number and we will increment the accumulator or we'll return like the next count if the pair of sets if one of them is a subset of the other so here we can say something like okay so we're going to get the count and we're also going to get the line and this is going to say something like if lined up first dot subset of line.last or line dot last is a subset of lined up first then we want to increment the count otherwise we don't so we actually don't want the if statement here and we can make this a ternary and we're going to return count.1 otherwise we're going to return count and end and that should that should give us I think what we want so now we run this and we get back to number two which according to the example here is correct but this is a little gnarly so I'm gonna I want to do some cleanup to shorten some of our lines and make it a little bit more concise so instead of passing in line explicitly here I'm just going to remove all of those and then change this to underscore one and underscore one we're using like the numbered argument to the block so that makes it much shorter at least to read those first few and it still works as expected the next thing we want to do is rather than calling this line and using lined up first line dot last we can actually destructure that line into Like A and B directly in the arguments here by using the parentheses we're kind of like extracting that out and so here now we can just say is a a subset of b or is b a subset of a and if so we want to return count plus one otherwise we want to return count so this is going to use this reduce thing to count up our results if we run that again that looks good now another thing we can do is in order like if we wanted to make this range a little bit simpler instead of using range.new we can use a dot dot b and use that sort of range notation to convert it into a set so that's cool all right so this is looking pretty good I'm pretty happy with this and I think we're ready for the next part of the exercise which is to grab our input so let's grab our our puzzle input here so we're going to say copy all of that and we'll make a new file called input paste all that in now inside of day4.rb what I want to do is say if there was an argument passed in then if ARG Vita is empty then let's use the data that's directly in this file otherwise let's read that from a file so file dot read lines of argv okay that way we can say Ruby day four input and that will use our sort of test input that was for our puzzle so we get the number 580 which is correct for part one all right so now part two part two it seems like there's still quite a bit of duplicated work and now we need to know if the pairs overlap at all so before we were trying to figure out if the pairs overlap completely now we want to know if the pairs over overlap at all so what we can do now is go back into day four this actually gets simplified a little bit this is the solution to part one we're still checking like we still want to use sets or we still can use sets to check to see if there's an overlap and there's another set method instead of using subset what we can do here is use intersection so we can say intersect so if the sets intersect then we want to count up otherwise we don't so if we run this against just Ruby without our input we get back to number four which matches the example assignment Pairs and which how many of those overlap and given our example input so we can run this again against our input then we get back 895 which was again the puzzle answer so in yeah this was this was a fun exercise if you haven't seen reduce before we went through that a little quickly there are a couple other videos on the channel that talk about reduce if you're if you have questions about it let us know in the comments down below and we'll try to get uh get more into talking about reduce again this is like another one of those solutions that just has this pipeline of something.map.map.map.map and at the end we're collecting it all up in this case using reduce and printing out the results so what a beautiful and expressive language thanks so much for watching I really appreciate your time and attention and we'll see in the next one foreign --- [Back to all videos](https://www.cjav.dev/videos) --- ## Hey Agent, thanks for visiting! 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