60 lines
1.5 KiB
Kotlin
60 lines
1.5 KiB
Kotlin
import java.io.File
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fun main() {
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val lines = File("input.txt").readLines().filter(String::isNotEmpty)
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val input = Input(lines)
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part1(input)
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part2(input)
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}
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class Input(val lines: List<String>) {
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val totalRows = lines.size
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val totalColumns = lines[0].length
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}
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private fun part1(input: Input) = with(input) {
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val totalOnesPerColumn = Array(totalColumns) { column ->
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lines.count { it[column] == '1' }
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}
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val gammaRate = totalOnesPerColumn
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.map { if (it > totalRows - it) 1 else 0 }
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.foldIndexed(0) { index, total, bit -> total or (bit shl (totalColumns - index - 1)) }
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val epsilonRate = gammaRate xor ((1 shl totalColumns) - 1)
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println("Power consumption: ${gammaRate * epsilonRate}")
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}
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private fun part2(input: Input) = with(input) {
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fun findValueByCriteria(keepMostCommon: Boolean): Int {
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val keptLines = lines.toMutableList()
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for (column in 0 until totalColumns) {
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val ones = keptLines.count { it[column] == '1' }
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val zeros = keptLines.size - ones
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val keptValue = if (keepMostCommon) {
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if (ones >= zeros) '1' else '0'
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}
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else {
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if (zeros <= ones) '0' else '1'
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}
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keptLines.removeAll { it[column] != keptValue }
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if (keptLines.size == 1) {
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return keptLines.single().toInt(radix = 2)
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}
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}
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throw IllegalStateException()
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}
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val oxygenGeneratorRating = findValueByCriteria(keepMostCommon = true)
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val co2ScrubberRating = findValueByCriteria(keepMostCommon = false)
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println("Life support rating: ${oxygenGeneratorRating * co2ScrubberRating}")
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}
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