Prepare for other years

2020-12-30 18:01:52 +01:00
parent 522618d106
commit 4a90257257
81 changed files with 277 additions and 253 deletions
@@ -0,0 +1,76 @@
+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 org.eclipse.collections.impl.factory.primitive.IntLists
+import org.eclipse.collections.impl.factory.primitive.IntSets
+
+@Day(8)
+class Day08(@Lines val input: Input<List<String>>) {
+
+    private val instructions = input.value.map {
+        val words = it.split(" ")
+        Instruction(Operation.valueOf(words[0].capitalize()), words[1].toInt())
+    }.toTypedArray()
+
+    fun part1() = run(instructions).let {
+        when (it) {
+            is VmResult.Looped -> it.acc
+            is VmResult.Terminated -> it.acc
+        }
+    }
+
+    private fun run(instructions: Array<Instruction>): VmResult {
+        var acc = 0
+        var ptr = 0
+
+        val visited = IntSets.mutable.empty()
+
+        while (visited.add(ptr)) {
+            val instruction = instructions[ptr]
+            when (instruction.operation) {
+                Operation.Acc -> {
+                    acc += instruction.argument
+                    ptr++
+                }
+                Operation.Jmp -> ptr += instruction.argument
+                Operation.Nop -> ptr++
+            }
+            if (ptr !in instructions.indices) {
+                return VmResult.Terminated(acc)
+            }
+        }
+
+        return VmResult.Looped(acc)
+    }
+
+    fun part2(): Int {
+        val possibleMutations = IntLists.mutable.empty()
+        instructions.forEachIndexed { i, e ->
+            if (e.operation == Operation.Jmp || e.operation == Operation.Nop) possibleMutations.add(i)
+        }
+
+        for (index in possibleMutations.toArray()) {
+            val copy = instructions.copyOf().also {
+                val modifiedOperation = if (it[index].operation == Operation.Nop) Operation.Jmp else Operation.Nop
+                it[index] = it[index].copy(operation = modifiedOperation)
+            }
+
+            val res = run(copy)
+            if (res is VmResult.Terminated) return res.acc
+        }
+
+        error("No result found")
+    }
+
+}
+
+private enum class Operation { Acc, Jmp, Nop }
+
+private data class Instruction(val operation: Operation, val argument: Int)
+
+private sealed class VmResult {
+    data class Looped(val acc: Int) : VmResult()
+    data class Terminated(val acc: Int) : VmResult()
+}