advent-of-code-2024/day9/part1.kts
2024-12-10 19:13:15 -07:00

76 lines
No EOL
2.2 KiB
Kotlin
Executable file

#!/usr/bin/env kotlin
import java.io.File
import java.util.*
import kotlin.math.min
data class ReplicatedData(
var fileId: Int?,
var times: Int,
)
val disk = File(if (args.size >= 1 && args[0] == "example") "./example.txt" else "./input.txt").readLines()[0]
// Parse into labeled sections
var id = 0
val parsed = LinkedList(disk.mapIndexed { i, char -> // I love linked lists i love linked lists i love linked lists
val num = char.digitToInt()
if (i % 2 == 0) {
// Every other starting with i = 0 should be real data
ReplicatedData(
fileId = i / 2,
times = num
)
} else {
ReplicatedData(
fileId = null,
times = num
)
}
}.filter { it.times != 0 })
val iter = parsed.listIterator()
var blocksFilled = 0
while (iter.hasNext()) {
val currentGroup = iter.next()
if (currentGroup.fileId != null || currentGroup.times < 1) continue
val (groupTakingFromIndex, groupTakingFrom) = parsed.asReversed()
.filter {it.times > 0 }
.withIndex()
.find { (_, it) -> it.fileId != null } ?: break
if (parsed.size - 1 - groupTakingFromIndex <= iter.nextIndex() - 1) break
val amountToMove = min(currentGroup.times, groupTakingFrom.times)
// Take the amount we are moving from the previous location
groupTakingFrom.times -= amountToMove
// And add it before the current one
val originalEmptySpace = currentGroup.times
iter.set(
ReplicatedData(
fileId = groupTakingFrom.fileId,
times = amountToMove
)
)
blocksFilled += amountToMove
// If we still have some left, insert back in the empty space and rewind the cursor
if (amountToMove < originalEmptySpace) {
iter.add(
ReplicatedData(
fileId = null,
times = originalEmptySpace - amountToMove
)
)
iter.previous() // Go back one so the next iteration of the loop will catch the new empty data we just added
}
}
println(
parsed
.filter { it.times > 0 && it.fileId != null }
.flatMap { group -> (1..group.times).map { _ -> group.fileId!! } }
.mapIndexed { i, data -> i.toULong() * data.toULong() }.sum()
)