a little 2019

advent/src/test/kotlin/org/elwaxoro/advent/y2019/Dec14.kt

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+package org.elwaxoro.advent.y2019
+
+import org.elwaxoro.advent.PuzzleDayTester
+import kotlin.math.ceil
+import kotlin.math.max
+import kotlin.math.min
+
+/**
+ * Day 14: Space Stoichiometry
+ */
+class Dec14 : PuzzleDayTester(14, 2019) {
+
+    private val stock = mutableMapOf<String, Long>()
+    private val recipes = loader()
+    private val trillion = 1000000000000
+
+    override fun part1(): Any = synthesize("FUEL", 1) == 654909L
+
+    /**
+     * Simple binary search, keep trying to synthesize until we're as close as we get
+     */
+    override fun part2(): Any {
+        var low = 0L
+        var high = trillion
+        while (low <= high) {
+            stock.clear()
+            val mid = (low + high) / 2
+            val created = synthesize("FUEL", mid)
+            if (created > trillion) {
+                high = mid - 1
+            } else if (created < trillion) {
+                low = mid + 1
+            } else {
+                return mid == 2876992L
+            }
+        }
+        return low - 1 == 2876992L
+    }
+
+    private fun synthesize(type: String, amount: Long): Long =
+        if (type == "ORE") {
+            // base case: getting ORE costs 1 per
+            amount
+        } else {
+            val available = takeStock(type, amount)
+            if (available == amount) {
+                // we have everything on hand already, zero additional cost
+                0
+            } else {
+                val need = amount - available
+                val (makes, costs) = recipes.getValue(type)
+                val repeat = ceil(need / makes.toDouble()).toInt()
+                val created = makes * repeat
+                // save the excess from creation
+                addStock(type, max(0, created - need))
+                // ok now actually make all the components
+                costs.sumOf { (makeType, makeAmount) -> synthesize(makeType, makeAmount * repeat) }
+            }
+        }
+
+    private fun addStock(type: String, count: Long) {
+        stock[type] = stock.getOrDefault(type, 0) + count
+    }
+
+    private fun takeStock(type: String, count: Long): Long {
+        val available = stock.getOrDefault(type, 0)
+        stock[type] = max(0, available - count)
+        return min(count, available)
+    }
+
+    private fun loader() = load().associate { line ->
+        val (inputRaw, outputRaw) = line.split(" => ")
+        val inputs = inputRaw.split(",").map { it.trim().split(" ").let { it[1] to it[0].toLong() } }
+        val (outAmt, outType) = outputRaw.split(" ")
+        outType to (outAmt.toLong() to inputs)
+    }
+}

advent/src/test/resources/2019/Dec14.txt

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+1 HKCVW, 2 DFCT => 5 ZJZRN
+8 TCPN, 7 XHTJF, 3 DFCT => 8 ZKCXK
+1 ZJZRN, 4 NZVL, 1 NJFXK, 7 RHJCQ, 32 MCQS, 1 XFNPT => 5 ZWQX
+10 DRWB, 16 JBHKV => 6 TCPN
+3 MBFK => 7 DRWB
+9 RHJCQ => 6 MBMKZ
+1 BVFPF => 2 KRTGD
+1 QNXC, 7 BKNQT, 1 XFNPT => 4 VNFJQ
+2 TCPN, 1 WFSV => 2 TGJP
+35 DFCT => 2 RHJCQ
+1 SKBV, 7 CTRH => 8 QGDSV
+8 VSRMJ, 1 BVFPF => 4 CTRH
+1 WMCD => 3 FPZLF
+13 CVJQG, 8 DXBZJ => 9 QBDQ
+1 XSRWM => 5 GDJGV
+132 ORE => 3 MBFK
+2 BQGP => 9 LZKJZ
+5 GZLHP => 7 WFSV
+2 RXSZS, 10 MBFK, 1 BPNVK => 2 GZLHP
+13 BZFH => 8 XSRWM
+3 QLSVN => 3 SKBV
+8 QBDQ => 4 VSRMJ
+1 RXSZS => 9 CVJQG
+3 MBFK => 3 BVFPF
+7 GZLHP, 4 MBFK, 5 CVJQG => 8 XHTJF
+1 GZLHP => 2 DFCT
+4 SZDWB, 4 RHJCQ, 1 WMCD => 3 RGZDK
+2 BRXLV => 8 DXBZJ
+192 ORE => 7 RXSZS
+1 PRMR, 6 DFCT => 5 SZDWB
+104 ORE => 9 BPNVK
+6 VLJWQ, 8 ZKCXK, 6 BKNQT, 26 JRXQ, 7 FPZLF, 6 HKCVW, 18 KRTGD => 4 RBFX
+7 XFNPT, 1 GDJGV => 2 HJDB
+15 SKBV, 8 DRWB, 12 RXSZS => 3 GHQPH
+1 BZFH => 5 GCBR
+1 TGJP, 6 SKBV => 1 BZFH
+4 KRTGD, 1 ZJHKP, 1 LZKJZ, 1 VNFJQ, 6 QBDQ, 1 PRMR, 1 NJFXK, 1 HJDB => 8 TFQH
+10 BVFPF, 1 RGZDK => 8 QNXC
+1 XHTJF => 5 JRXQ
+3 XKTMK, 4 QGDSV => 3 ZJHKP
+2 BZFH => 7 PRMR
+1 BPNVK, 1 RXSZS => 5 JBHKV
+10 XHTJF => 9 BKNQT
+1 JBHKV, 2 XHTJF => 8 QLSVN
+24 VNFJQ, 42 TFQH, 39 RBFX, 1 ZWQX, 7 VBHVQ, 26 DRWB, 21 NJFXK => 1 FUEL
+26 WBKQ, 14 XHTJF => 5 BQGP
+5 WBKQ, 7 MBMKZ => 3 LQGC
+6 LQGC => 5 NZVL
+13 KRTGD, 5 GHQPH => 9 VLJWQ
+117 ORE => 4 BRXLV
+3 XKTMK, 1 PRMR => 2 MCQS
+3 DRWB, 7 BVFPF, 4 TCPN => 7 NJFXK
+10 VHFCR, 13 JZQJ => 5 XKTMK
+17 CVJQG, 4 GCBR => 9 HKCVW
+22 DFCT, 17 TGJP => 2 WBKQ
+2 JZQJ, 12 XFNPT, 1 BQGP => 2 VBHVQ
+12 HKCVW => 1 JZQJ
+1 XSRWM => 3 WMCD
+12 BZFH, 14 SKBV, 1 CTRH => 4 XFNPT
+7 ZKCXK => 6 VHFCR