Add solution for Y2024D13.

Author: Jadarma

Diff for: README.md

@@ -15,7 +15,7 @@ _"Anything that's worth doing, is worth overdoing."_
 Table of contents to jump straight to the problem you're looking for.
 
 <details open>
-    <summary>2024 (24x⭐)</summary>
+    <summary>2024 (26x⭐)</summary>
 
 | Day | Title                                                      | Stars |
 |:---:|:-----------------------------------------------------------|:-----:|
@@ -31,6 +31,7 @@ Table of contents to jump straight to the problem you're looking for.
 | 10  | [Hoof It](solutions/aockt/y2024/Y2024D10.kt)               |  ⭐⭐   |
 | 11  | [Plutonian Pebbles](solutions/aockt/y2024/Y2024D11.kt)     |  ⭐⭐   |
 | 12  | [Garden Groups](solutions/aockt/y2024/Y2024D12.kt)         |  ⭐⭐   |
+| 13  | [Claw Contraption](solutions/aockt/y2024/Y2024D13.kt)      |  ⭐⭐   |
 
 </details>
 

Diff for: inputs/aockt/y2024/d13/input.txt

@@ -0,0 +1,54 @@
+package aockt.y2024
+
+import aockt.util.parse
+import aockt.util.spacial.Point
+import io.github.jadarma.aockt.core.Solution
+
+object Y2024D13 : Solution {
+
+    /**
+     * The configuration of a crane machine. The arm starts at the [Point.Origin].
+     * @property prize The coordinate of the prize.
+     * @property a     The delta the arm will move when pressing the A button.
+     * @property b     The delta the arm will move when pressing the B button.
+     */
+    private data class CraneMachine(val prize: Point, val a: Point, val b: Point) {
+        init {
+            require(listOf(prize.x, prize.y, a.x, a.y, b.x, b.y).all { it > 0 }) { "Crane values must be positive." }
+            require(a != b) { "Crane buttons A and B must have different offsets." }
+        }
+
+        /** The total tokens required to play and win, or `null` if the machine is rigged and there is no solution. */
+        val costToSolve: Long? by lazy {
+            // Explanation: To win, we need to find integer solutions n and m such that:
+            // a.x * n + b.x * m == prize.x and a.y * n + b.y * m == prize.y
+            // Solving it on paper gives us the following formulas:
+            val n = (prize.x * b.y - prize.y * b.x).toDouble() / (a.x * b.y - b.x * a.y)
+            val m = (prize.x - a.x * n) / b.x
+            if (n % 1 != 0.0 || m % 1 != 0.0) null
+            else n.toLong() * 3 + m.toLong()
+        }
+    }
+
+    /**
+     * Parse the [input] and return the configurations of the [CraneMachine]s.
+     * If [extraLong], will move the prize very far away.
+     */
+    private fun parseInput(input: String, extraLong: Boolean): List<CraneMachine> = parse {
+        val regex = Regex("""Button A: X\+(\d+), Y\+(\d+)\nButton B: X\+(\d+), Y\+(\d+)\nPrize: X=(\d+), Y=(\d+)""")
+        val prizeDelta = if (extraLong) 10_000_000_000_000L else 0L
+        input
+            .split("\n\n")
+            .map { regex.matchEntire(it)!!.destructured }
+            .map { (ax, ay, bx, by, px, py) ->
+                CraneMachine(
+                    prize = Point(px.toLong() + prizeDelta, py.toLong() + prizeDelta),
+                    a = Point(ax.toLong(), ay.toLong()),
+                    b = Point(bx.toLong(), by.toLong()),
+                )
+            }
+    }
+
+    override fun partOne(input: String): Long = parseInput(input, false).mapNotNull(CraneMachine::costToSolve).sum()
+    override fun partTwo(input: String): Long = parseInput(input, true ).mapNotNull(CraneMachine::costToSolve).sum()
+}

Diff for: inputs/aockt/y2024/d13/solution_part1.txt

@@ -0,0 +1,29 @@
+package aockt.y2024
+
+import io.github.jadarma.aockt.test.AdventDay
+import io.github.jadarma.aockt.test.AdventSpec
+
+@AdventDay(2024, 13, "Claw Contraption")
+class Y2024D13Test : AdventSpec<Y2024D13>({
+
+    val exampleInput = """
+        Button A: X+94, Y+34
+        Button B: X+22, Y+67
+        Prize: X=8400, Y=5400
+
+        Button A: X+26, Y+66
+        Button B: X+67, Y+21
+        Prize: X=12748, Y=12176
+
+        Button A: X+17, Y+86
+        Button B: X+84, Y+37
+        Prize: X=7870, Y=6450
+
+        Button A: X+69, Y+23
+        Button B: X+27, Y+71
+        Prize: X=18641, Y=10279
+    """.trimIndent()
+
+    partOne { exampleInput shouldOutput 480 }
+    partTwo { exampleInput shouldOutput 875_318_608_908 }
+})