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Day 22 kotliniziation for more concise code.

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Chris Hodges 2024-12-22 18:58:31 +01:00
parent 343414cd04
commit e222975b2a
1 changed files with 20 additions and 35 deletions
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55
src/aoc2024/Day22.kt
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@ -27,58 +27,43 @@ fun main() {
2024
"""
fun next(number: Int): Int {
val r1 = (number xor (number shl 6)) and 0xff_ff_ff
val r2 = (r1 xor (r1 shr 5)) and 0xff_ff_ff
val r3 = (r2 xor (r2 shl 11)) and 0xff_ff_ff
return r3
fun priceSequence(seed: Int) = generateSequence(seed) {
val r1 = (it xor (it shl 6)) and 0xff_ff_ff
val r2 = r1 xor (r1 shr 5)
(r2 xor (r2 shl 11)) and 0xff_ff_ff
}
fun part1(input: List<String>): Long {
var sum = 0L
for (i in input.map(String::toInt)) {
var v = i
for (p in 1..2000) {
v = next(v)
}
sum += v
}
return sum
}
fun part1(input: List<String>) =
input.map(String::toInt).sumOf { priceSequence(it).elementAt(2000).toLong() }
fun part2(input: List<String>): Int {
val normalStrings = ArrayList<String>(2500)
val deltaStrings = ArrayList<String>(2500)
for (i in input.map(String::toInt)) {
val strings = input.map(String::toInt).map {
val normalString = StringBuffer(2024)
val deltaString = StringBuffer(2024)
var v = i
var lastd = v % 10
for (p in 1..2000) {
v = next(v)
val d = v % 10
var lastd = it % 10
priceSequence(it).take(2001).forEach {
val d = it % 10
val delta = d - lastd
normalString.append(d)
deltaString.append('j' + delta)
lastd = d
}
normalStrings.add(normalString.toString())
deltaStrings.add(deltaString.toString())
deltaString.toString() to normalString.toString()
}
// it's not my fault that brute force is still working
// note that there are less than 19^4 valid combinations, but we don't care
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
val token = StringBuffer(4)
.append('a' + (it / (19 * 19 * 19)))
.append('a' + ((it / (19 * 19)) % 19))
.append('a' + ((it / 19) % 19))
.append('a' + ((it % 19))).toString()
strings.sumOf {
val idx = it.first.indexOf(token)
if (idx >= 0) it.second[idx + 3].digitToInt() else 0
}
}
}.awaitAll().max()