Add Day17

src/main/kotlin/Day17.kt

@@ -0,0 +1,144 @@
+import kotlin.math.pow
+import utils.AoCDay
+import utils.chunkedInput
+import utils.mapInner
+import utils.mapToLong
+import utils.splitAndMapToLong
+
+class Day17 : AoCDay() {
+    val chunks = input.chunkedInput().mapInner { it.split(": ")[1] }
+    val registers = chunks[0].mapToLong().toMutableList()
+    val instructions = chunks[1].splitAndMapToLong(",").flatten()
+
+    override fun part1(): Any {
+        return executeProgram().joinToString(",")
+    }
+
+    override fun part2(): Any {
+        return matchOutput(instructions, instructions)
+    }
+
+    private fun matchOutput(program: List<Long>, goal: List<Long>): Long {
+        val multiplier = if (goal.size == 1) 0 else 8 * matchOutput(program, goal.subList(1, goal.size))
+        return multiplier.let { start ->
+            generateSequence(start) { it + 1 }.first { executeProgram(it) == goal }
+        }
+    }
+
+    fun executeProgram(overwriteA: Long = registers[0]): List<Long> {
+        val registers = mutableListOf(overwriteA, this.registers[1], this.registers[2])
+        registers[0] = overwriteA
+        var instructionPointer = 0
+        val output = mutableListOf<Long>()
+        while (true) {
+            if (instructionPointer >= instructions.size) break
+            val instruction = instructions[instructionPointer]
+            when (instruction) {
+                0L -> {
+                    val comboOperand = instructions[instructionPointer + 1]
+                    val power = 2.0.pow(getComboMeaning(registers, comboOperand).toDouble()).toLong()
+                    val result = registers[0] / power
+                    registers[0] = result
+                    instructionPointer += 2
+                }
+
+                1L -> {
+                    val literalOperand = instructions[instructionPointer + 1]
+                    registers[1] = registers[1] xor literalOperand
+                    instructionPointer += 2
+                }
+
+                2L -> {
+                    val comboOperand = instructions[instructionPointer + 1]
+                    val modulo = getComboMeaning(registers, comboOperand) % 8
+                    registers[1] = modulo
+                    instructionPointer += 2
+                }
+
+                3L -> {
+                    if (registers[0] == 0L) {
+                        instructionPointer += 2
+                        continue
+                    }
+                    val literalOperand = instructions[instructionPointer + 1]
+                    instructionPointer = literalOperand.toInt()
+                }
+
+                4L -> {
+                    registers[1] = registers[1] xor registers[2]
+                    instructionPointer += 2
+                }
+
+                5L -> {
+                    val comboOperand = instructions[instructionPointer + 1]
+                    output += getComboMeaning(registers, comboOperand) % 8L
+                    instructionPointer += 2
+                }
+
+                6L -> {
+                    val comboOperand = instructions[instructionPointer + 1]
+                    val power = 2.0.pow(getComboMeaning(registers, comboOperand).toDouble()).toLong()
+                    val result = registers[0] / power
+                    registers[1] = result
+                    instructionPointer += 2
+                }
+
+                7L -> {
+                    val comboOperand = instructions[instructionPointer + 1]
+                    val power = 2.0.pow(getComboMeaning(registers, comboOperand).toDouble()).toLong()
+                    val result = registers[0] / power
+                    registers[2] = result
+                    instructionPointer += 2
+                }
+            }
+        }
+        return output
+    }
+
+    fun getComboMeaning(registers: List<Long>, operand: Long): Long {
+        return when (operand) {
+            0L -> 0L
+            1L -> 1L
+            2L -> 2L
+            3L -> 3L
+            4L -> registers[0]
+            5L -> registers[1]
+            6L -> registers[2]
+            else -> error("Invalid operand $operand")
+        }
+    }
+
+}
+
+fun main() {
+    Day17().execute()
+}
+
+/*
+
+2,4,1,2,7,5,1,3,4,3,5,5,0,3,3,0
+
+2, 4:
+reg[B] = reg[A] % 8
+
+1, 2:
+reg[B] = reg[B] xor 2
+
+7, 5:
+reg[C] = reg[A] % 8
+
+1, 3:
+reg[B] = reg[B] xor 3
+
+4, 3:
+reg[B] = reg[B] xor reg[C]
+
+5, 5:
+output += reg[B] % 8
+
+0, 3:
+reg[A] = reg[A] / 8
+
+3, 0:
+if (reg[A] != 0) goto 0
+ */