Use a `LinkedList` instead of a `.toMutableList()`...

# advent-of-code

[karelpeeters]

Use a LinkedList instead of a .toMutableList() ArrayList.

[szymen]

I don't understand it, but when I change it to LinkedList, performance is worser. In all cases.

[szymen]

I mean that I tried to replace ArrayList with LinkedList in all places (both in main function and in part2 implementation), and always it causes problems with performance.

[karelpeeters]

You literally changed line 23 to create a linkedlist?

[szymen]

I changed polymer.toMutableList() to LinkedList(polymer) in line 23.

[karelpeeters]

Can you quickly share your buid.gradle for the coroutine stuff?

[szymen]

I've added also measuring like this:

fun main(args: Array<String>) {
    val time = measureTimeMillis {
        val input = File("input5.txt").readText()
        val currentPolymer = input.toCharArray().toMutableList()
        println(Day5.part1(currentPolymer))
        println(Day5.part2(currentPolymer))
    }
    println(time)
}

And version with LinkedList is about 2 times slower

[szymen]

@karelpeeters It's default build.gradle file generated for gradle project by Intellij. The only thing I added was:

implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.0.1'

[szymen]

Also part1 is much slower when I use LinkedList in 10 line.

[karelpeeters]

Yeah it's the same for me when I run your code.

[karelpeeters]

Which is really strange since I have about the same code here: https://kotlinlang.slack.com/archives/C87V9MQFK/p1544022734125600

[karelpeeters]

I'm going to bed now, I'll experiment a bit with it tomorrow simple smile

[hudsonb]

ArrayList generally outperforms LinkedList

[pavel]

If you want to go faster, keep ArrayList, but start in the end of the list instead of the beginning

[pavel]

this will take constant time with arraylist, but linear time with linkedlist

[karelpeeters]

Nice, thanks for finding it!