Day 13. Wrong bet on dynamic programming for part 1.

src/aoc2024/Day13.kt

@@ -0,0 +1,110 @@
+package aoc2024
+
+import println
+import readInput
+
+/*
+--- Day 13: Claw Contraption ---
+https://adventofcode.com/2024/day/13
+*/
+fun main() {
+
+    val inlineTestInput = """
+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
+"""
+
+    fun part1(input: List<String>): Int {
+        var i = 0
+        var sum = 0
+        while (i < input.size) {
+            val (ax, ay) = "Button A: X\\+(\\d+), Y\\+(\\d+)".toRegex().find(input[i++])!!.groupValues.drop(1).map { it.toInt() }
+            val (bx, by) = "Button B: X\\+(\\d+), Y\\+(\\d+)".toRegex().find(input[i++])!!.groupValues.drop(1).map { it.toInt() }
+            val (px, py) = "Prize: X=(\\d+), Y=(\\d+)".toRegex().find(input[i++])!!.groupValues.drop(1).map { it.toInt() }
+            i++
+            val xpos = IntArray(101 * 101)
+            val ypos = IntArray(101 * 101)
+            val solutions = ArrayList<Int>()
+            for (b in 1..100) {
+                for (a in 1..100) {
+                    val op = (a - 1) + (b - 1) * 101
+                    if ((xpos[op] == px) && (ypos[op] == py)) {
+                        solutions.add(op)
+                    }
+                    if ((xpos[op] > px) || (ypos[op] > py)) break
+                    xpos[a + (b - 1) * 101] = xpos[op] + ax
+                    xpos[(a - 1) + b * 101] = xpos[op] + bx
+                    ypos[a + (b - 1) * 101] = ypos[op] + ay
+                    ypos[(a - 1) + b * 101] = ypos[op] + by
+                }
+            }
+            val minTokens = solutions.minOfOrNull { (it % 101) * 3 + (it / 101) }
+            sum += minTokens ?: 0
+        }
+        return sum
+    }
+
+    fun part2(input: List<String>): Long {
+        var i = 0
+        var sum = 0L
+
+        // 1. ax * pa + bx * pb = px
+        // 2. ay * pa + by * pb = py
+        // 3. pa * 3 + pb <- min
+        // 4. pa, pb in N (int > 0)
+
+        // ax * pa + bx * pb - px = ay * pa + by * pb - py
+        // (ax - ay) * pa + (bx - by) * pb + py - px = 0
+        // (ax - ay) * pa + (bx - by) * pb = px - py
+
+        while (i < input.size) {
+            val (ax, ay) = "Button A: X\\+(\\d+), Y\\+(\\d+)".toRegex().find(input[i++])!!.groupValues.drop(1).map { it.toLong() }
+            val (bx, by) = "Button B: X\\+(\\d+), Y\\+(\\d+)".toRegex().find(input[i++])!!.groupValues.drop(1).map { it.toLong() }
+            val (px, py) = "Prize: X=(\\d+), Y=(\\d+)".toRegex().find(input[i++])!!.groupValues.drop(1).map { it.toLong() + 10000000000000L }
+            i++
+
+//            val t1 = ax - ay
+//            val t2 = bx - by
+//            val t3 = px - py
+
+            val pad = (px * by - py * bx)
+            val pan = (ax * by - ay * bx)
+            if (pad % pan == 0L) {
+                val pa = pad / pan
+                val pbd = (px - pa * ax)
+                if (pbd % bx == 0L) {
+                    val pb = pbd / bx
+                    sum += pa * 3 + pb
+                }
+            }
+        }
+        return sum
+    }
+
+    // test if implementation meets criteria from the description, like:
+    val testInput = inlineTestInput.trim().reader().readLines()
+    //val testInput = readInput("aoc2024/Day13_test")
+    val testInputPart1Result = part1(testInput)
+    println("Part 1 Test: $testInputPart1Result")
+    val testInputPart2Result = part2(testInput)
+    println("Part 2 Test: $testInputPart2Result")
+    check(testInputPart1Result == 480)
+    //check(testInputPart2Result == 0L)
+
+    val input = readInput("aoc2024/Day13")
+    part1(input).println()
+    part2(input).println()
+}