And we're off! Are there any specific rules in this channel about spoilers? My solutions and performance measurements can be found at https://github.com/jorispz/aoc-2018, and I'll be posting the performance results in a thread from this message for those who are interested

okay, finished day 2 part 2, my partTwo function takes around 70 ms

Shall we make a thread for discussing

Day 2 - Inventory Management System

?

OK, here's mine. Quite a bit different (probably a lot slower): https://github.com/tginsberg/advent-2018-kotlin/blob/master/src/main/kotlin/com/ginsberg/advent2018/Day02.kt

I usually just run them from tests so my times are weird. If I don't do that I get 16/47

No Matter How You Slice It — Day 3, Part 1

Hmm this makes me wonder: does

groupingBy

have any use cases other than

eachCount

?

@robin And I think you can replace

claims.map { it.cells }.reduce { ... }

with

claims.flatMap { }

.

Finally at the 2nd try 😁

What is this

@Regex

sorcery!?

in the challenge today i iterated through the claims and their cells twice:

claims.forEach { claim ->
    for (row in claim.x until claim.x + claim.width) {
        for (col in claim.y until claim.y + claim.height) {
            countArray[row][col] = countArray[row][col] + 1
        }
    }
}

println("part 1: ${countArray.flatMap { it.asIterable() }.count { it > 1 }}")

claims.forEach { claim ->
    for (row in claim.x until claim.x + claim.width) {
        for (col in claim.y until claim.y + claim.height) {
            if (countArray[row][col] != 1) {
                return@forEach
            }
        }
    }
    println("part 2: ${claim.id}")
}

i don't really want to change the approach, but is there a nicer way of iterating?

Day four was tough! Here's my solution: https://github.com/devbridie/adventofcode2018/blob/master/src/main/kotlin/com/devbridie/adventofcode2018/solutions/Day4.kt

Hey, welcome. Can you help me understand a bit more about what you are asking. Are you asking why you would do that or how to do it?

This is my today's attempt, but the web says my answer is wrong. I am pretty confident I should have it right, but I have no idea what is wrong though :-)), so it seems I am stuck for now ...

Hey, those who are measuring time with native, do you run release bits?

Spoiler Day 5 Solution: https://gitlab.com/abowes/adventofcode2018/blob/master/src/main/kotlin/jfactory/day05/Polymer.kt

I'm pretty happy with my solution today. One pass on each polymer string. 🙂 https://github.com/tginsberg/advent-2018-kotlin/blob/master/src/main/kotlin/com/ginsberg/advent2018/Day05.kt

Finally came up with a solution, however not really idiomatic (you can tell I come from Python 😉 ) https://github.com/DnzzL/kotlin-advent-2018/blob/master/src/main/kotlin/tech/thomaslegrand/advent2018/Day05.kt

Part 2 could definitely use some parallelism to speed up destroying the units and what-not, but I can't figure out how to do it. I've never worked with coroutines, and this parallel map function I found and pasted in my code doesn't seem to work, everything still happens sequentially. https://jivimberg.io/blog/2018/05/04/parallel-map-in-kotlin/

I think we can further reduce the iterations in day 5 part 2 by using the result from part 1 as well as only using the set of alphabets in the polymer instead of going fro A..Z

Use a

LinkedList

instead of a

.toMutableList()

ArrayList

.

Today reminded me that I don't care for puzzles involving grids. Ugly datastructures, inefficient loops - bleh. But, this is as good as I can make it: https://github.com/jorispz/aoc-2018/blob/master/src/commonMain/kotlin/P06.kt Performance is quite abysmal (first/best of 25 runs as usual): JVM

1159/270 ms

, JS

3692/3002 ms

, native

15513/12944 ms

My test pass but not the answer, worst feeling ever 😅 must have a wrong assumption

-.kt

My flailing around has yielded a proper solution to the example on step 2, but not for the actual, and I just think maybe I don't get it.

I’ve been going along in rust this year, but graphs are hard in rust, so I’m considering doing kotlin for day 6.

I think this solution for day 7 part 1 is optimal. SPOILERS INSIDE

Now this one was pretty tough for me. Took me like 4h or more to solve both parts. Good I have vacation until the end of year, so I have time to fiddle with it 😄

I still feel like I can get this cleaner. I did try to write one function to do both parts and just change the workers and costing function, but abandoned that because it didn't immediately work, and I'm not convinced I can explain it succinctly when I blog about it later.