Please tell me there isn’t a String.toList

I posted this in the solution thread, but since it's actually a question, I'll post it here too ⚠️ SPOILERS ⚠️

For the last three years I have used Kotlin MPP to do AoC. One thing that always slightly bothered me was that, because there is no common File api, I had to resort to putting the input directly in the source code. Today I finally took some time to attempt to read my input from a file instead. My needs are simple: I want to put a file with inputs in a shared resources directory, say

src\commonMain\resources\day01.txt

and read its contents as text in my solutions. This isn't trivial in Kotlin multi-platform, as a.) there isn't a common file API, and b.) only the JVM provides standardized access to the resources directory. To deal with this platform-dependent stuff, Kotlin MPP offers the `expect`/`actual` mechanism. In common code, I declare that each target platform (JVM, Node and native) should offer a

readInput

function:

expect fun readInput(name: String): String

The, each platform can implement this in a platform-specific way: JVM:

actual fun readInput(name: String) = {}::class.java.getResource(name).readText()

Since Node and native don't get access to the resources directory, I use an enviroment variable

AOC_INPUT_DIR

to define the directory where they should look for the input files. Their implementations then become: Node:

external fun require(name: String): dynamic
val fs = require("fs")
val path = require("path")

actual fun readInput(name: String): String {
    val path = path.join(process.env.AOC_INPUT_DIR, name)
    return fs.readFileSync(path, "utf8") as String
}

Native:

actual fun readInput(name: String): String {
    val returnBuffer = StringBuilder()
    val inputDir = getenv("AOC_INPUT_DIR")?.toKString() ?: ""
    val file = fopen("""$inputDir\$name""", "r") ?: throw IllegalArgumentException("Cannot open input file $name")

    try {
        memScoped {
            val readBufferLength = 64 * 1024
            val buffer = allocArray<ByteVar>(readBufferLength)
            var line = fgets(buffer, readBufferLength, file)?.toKString()
            while (line != null) {
                returnBuffer.append(line)
                line = fgets(buffer, readBufferLength, file)?.toKString()
            }
        }
    } finally {
        fclose(file)
    }

    return returnBuffer.toString()
}

I'm not sure I'm actually going to use this, I don't really mind having the input in the source, but at least I know how to do it now 🙂

⚠️ Day 7 Solution Thread  ⚠️

It says my answer for part 1 is wrong but I just don't see my mistake

I have been discussing with a friend and I wonder what your views are: He uses extension-functions more often than me. E.g. on Day03 (Slopes/Trees), he used an extension function on 'String' to check a coordinate (including the 'wrapping') if it is a tree or not. I used a regular function. On Day01 we both used extension-functions e.g. on Pair to to define a .sum(). So when is it a good idea to use extension functions and when not?

Mild spoilers in thread; mutable vs functional style for a non-trivial data transformation, curious to see which people think is more readable

Spoil alert in that thread. (graphical depiction of part of the data structure)

⚠️ Day 8 Solution Thread  ⚠️

I'll do that tomorrow I was writting a travelling salesman for day 9 of 2015…

I saw the input for today before I read the problem and I went OH NO! Not IntCode again!! And then I saw it was a lot simpler. (for now)

For a moment I didn't comprehend that the you can only change the kind of instruction, not the argument. I thought you could change both

and i was just like wtf, how on earth would you do that

For those curious, a better algorithmic solution for day 8 part b, way too lazy to implement, see thread

graph based maybe?

Question for the channel: Do you time-box the question before calling it quits? or do you spend as much time as needed to get to the answer? specially around the latter more difficult questions

semi related, for those who want to see an O(N) solution for part b), see thread

Hi, I'm in Day7 part 1. I have the right algo for the example input, but not with the real input, I didn't see how to investigate that, other people having the same issue ? What I have missed ?

⚠️ Day 9 Solution Thread  ⚠️

Do you get a star for solving after 24hrs?

‼️*Day 10 Solution Thread* ⁉️

ok that was… wow (spoilers)

Conway would have liked it

❕Day 11 Solution Thread❣️

Man people are fast. This si the only day I'v emade a half legitimate attempt at starting right at midnight

Took me about 15-20 minutes all in all, but the solution is not efficient at all, 700ms for the whole thing.

Hey everyone. I have not yet solved Day7 yet. I want to bang my head against it for a little longer before I look up other solutions. But so far I am building Regex, nested with Regex, which match stuff split with more Regex… and so on. xD At the end, I am building BagRule objects that I can then traverse and check. But I belive there must be a more elegant way to parse the string into one of the objects I defined. Like specifying a grammar in a more elegant form than just Regex. With named elements that are easier to put into an object. Is there some library or something you could suggest? Other than that, I could express everything in one Regex. But the matching groups would be nested, I have no idea how to work with that. My mind was already blown 2-3 days before Day 7 when I found

destructed

😛

Day 12 solution thread