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Refresher on Coroutines for maximum parallel brute force for Day 22.

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Chris Hodges 2024-12-22 18:42:55 +01:00
parent bc542bd29c
commit 343414cd04
1 changed files with 18 additions and 19 deletions
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37
src/aoc2024/Day22.kt
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@ -1,5 +1,9 @@
package aoc2024
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.async
import kotlinx.coroutines.awaitAll
import kotlinx.coroutines.runBlocking
import println
import readInput
@ -50,7 +54,6 @@ fun main() {
val deltaString = StringBuffer(2024)
var v = i
var lastd = v % 10
normalString.append(lastd)
for (p in 1..2000) {
v = next(v)
val d = v % 10
@ -64,26 +67,22 @@ fun main() {
}
// it's not my fault that brute force is still working
val tokenBuffer = StringBuffer(5)
tokenBuffer.append(" ")
val maxIdx = deltaStrings[0].length - 3
var maxBananas = 0
for (code in 0 until 19 * 19 * 19 * 19) {
tokenBuffer.setCharAt(0, 'a' + (code / (19 * 19 * 19)))
tokenBuffer.setCharAt(1, 'a' + ((code / (19 * 19)) % 19))
tokenBuffer.setCharAt(2, 'a' + ((code / 19) % 19))
tokenBuffer.setCharAt(3, 'a' + ((code % 19)))
var bananas = 0
val token = tokenBuffer.toString()
for (i in deltaStrings.indices) {
val idx = deltaStrings[i].indexOf(token)
if (idx in 0..maxIdx) {
bananas += normalStrings[i][idx + 4].digitToInt()
return runBlocking {
(0..(19 * 19 * 19 * 19)).map {
async(Dispatchers.Default) {
val tokenBuffer = StringBuffer(4)
tokenBuffer.append('a' + (it / (19 * 19 * 19)))
tokenBuffer.append('a' + ((it / (19 * 19)) % 19))
tokenBuffer.append('a' + ((it / 19) % 19))
tokenBuffer.append('a' + ((it % 19)))
val token = tokenBuffer.toString()
deltaStrings.indices.sumOf {
val idx = deltaStrings[it].indexOf(token)
if (idx >= 0) normalStrings[it][idx + 3].digitToInt() else 0
}
}
}
maxBananas = maxBananas.coerceAtLeast(bananas)
}.awaitAll().max()
}
return maxBananas
}
// test if implementation meets criteria from the description, like: