Day14

2020-12-14 10:09:08 +01:00
parent d12618febd
commit 1850a2145c
2 changed files with 658 additions and 0 deletions
@@ -0,0 +1,99 @@
+package be.vandewalleh.aoc.days
+
+import be.vandewalleh.aoc.utils.input.Day
+import be.vandewalleh.aoc.utils.input.Input
+import be.vandewalleh.aoc.utils.input.Lines
+import be.vandewalleh.aoc.utils.input.createDay
+import kotlin.math.pow
+import org.eclipse.collections.impl.factory.primitive.IntObjectMaps
+import org.eclipse.collections.impl.factory.primitive.ObjectLongMaps
+
+@Day(14)
+class Day14(@Lines val input: Input<List<String>>) {
+
+    private val memRe = "mem\\[(\\d+)] = (.*)$".toRegex()
+
+    private fun Long.toBin36() = toString(2).padStart(length = 36, padChar = '0')
+
+    fun part1(): Long {
+        val mem = IntObjectMaps.mutable.empty<String>()
+
+        var currentMask: String = ""
+
+        for (line in input.value) {
+            if (line.startsWith("mask")) {
+                currentMask = line.removePrefix("mask = ")
+            } else {
+                val (address, value) = memRe.find(line)!!.destructured
+                val bin = value.toLong().toBin36()
+
+                val result = bin.zip(currentMask)
+                    .map { (bin, mask) -> if (mask != 'X') mask else bin }
+                    .joinToString("")
+
+                mem.put(address.toInt(), result)
+            }
+        }
+
+        return mem.values()
+            .map { it.dropWhile { it == '0' } }
+            .map { it.toLong(2) }
+            .sum()
+    }
+
+    fun part2(): Long {
+        val mem = ObjectLongMaps.mutable.empty<String>()
+
+        var currentMask: String = ""
+
+        for (line in input.value) {
+            if (line.startsWith("mask")) {
+                currentMask = line.removePrefix("mask = ")
+            } else {
+                val (address, value) = memRe.find(line)!!.destructured.let { (add, value) ->
+                    add.toLong().toBin36() to value.toLong()
+                }
+
+                val addresses = address.zip(currentMask).map { (address, mask) ->
+                    when (mask) {
+                        'X' -> arrayOf('0', '1')
+                        '1' -> arrayOf('1')
+                        else -> arrayOf(address)
+                    }
+                }
+
+                val mutations = currentMask.count { it == 'X' }.let { 2.0.pow(it.toDouble()).toInt() }
+                val builders = Array(mutations) { StringBuilder() }
+
+                var groups = 1
+
+                for (address in addresses) {
+                    if (address.size > 1) {
+                        groups *= 2
+                        val groupSize = mutations / groups
+                        var j = 0
+                        for (i in 0 until mutations) {
+                            val flip = i % groupSize == 0
+                            if (flip) j = if (j == 0) 1 else 0
+                            builders[i].append(address[j])
+                        }
+                    } else {
+                        builders.forEach { it.append(address[0]) }
+                    }
+                }
+
+                builders.map { it.toString() }.forEach { address ->
+                    mem.put(address, value)
+                }
+            }
+        }
+
+        return mem.values().sum()
+    }
+
+}
+
+fun main() = with(createDay<Day14>()) {
+    println(part1())
+    println(part2())
+}