34 lines
1.1 KiB
Kotlin
34 lines
1.1 KiB
Kotlin
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val regex = "Button A: X\\+(\\d+), Y\\+(\\d+)\nButton B: X\\+(\\d+), Y\\+(\\d+)\nPrize: X=(\\d+), Y=(\\d+)".toRegex()
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data class Machine(
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val buttonA: Grid.Coordinate,
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val buttonB: Grid.Coordinate,
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val price: Grid.Coordinate
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) {
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fun solveA(b: Int) = (price.x - b * buttonB.x) / buttonA.x
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fun solveB() = (price.y * buttonA.x - price.x * buttonA.y) / (buttonA.x * buttonB.y - buttonA.y * buttonB.x)
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fun solve(): Pair<Int, Int>? {
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val b = solveB()
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val a = solveA(b)
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return Pair(a, b).takeIf { (a * buttonA.x + b * buttonB.x) == price.x && (a * buttonA.y + b * buttonB.y) == price.y }
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}
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}
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fun main() {
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val part1 = regex.findAll(readInputString("day13.txt"))
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.map {
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Machine(
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buttonA = Grid.Coordinate(it.groupValues[1].toInt(), it.groupValues[2].toInt()),
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buttonB = Grid.Coordinate(it.groupValues[3].toInt(), it.groupValues[4].toInt()),
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price = Grid.Coordinate(it.groupValues[5].toInt(), it.groupValues[6].toInt()),
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)
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}
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.mapNotNull { it.solve() }
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.sumOf { (a, b) -> 3 * a + b }
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println("Part 1: $part1")
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}
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