Solved day 17

README.md

@@ -32,7 +32,7 @@ _My solutions to the 2024 edition of [Advent of Code](https://adventofcode.com/2
 | **[14](https://adventofcode.com/2024/day/14)** | [solution](src/main/scala/adventofcode/solutions/Day14.scala) |
 | **[15](https://adventofcode.com/2024/day/15)** | [solution](src/main/scala/adventofcode/solutions/Day15.scala) |
 | **[16](https://adventofcode.com/2024/day/16)** | [solution](src/main/scala/adventofcode/solutions/Day16.scala) |
-| **[17](https://adventofcode.com/2024/day/17)** | [](src/main/scala/adventofcode/solutions/Day17.scala) |
+| **[17](https://adventofcode.com/2024/day/17)** | [solution](src/main/scala/adventofcode/solutions/Day17.scala) |
 | **[18](https://adventofcode.com/2024/day/18)** | [](src/main/scala/adventofcode/solutions/Day18.scala) |
 | **[19](https://adventofcode.com/2024/day/19)** | [](src/main/scala/adventofcode/solutions/Day19.scala) |
 | **[20](https://adventofcode.com/2024/day/20)** | [](src/main/scala/adventofcode/solutions/Day20.scala) |

input/17.txt

@@ -0,0 +1,5 @@
+Register A: 44374556
+Register B: 0
+Register C: 0
+
+Program: 2,4,1,5,7,5,1,6,0,3,4,1,5,5,3,0

output/17-1.txt

@@ -0,0 +1 @@
+1,5,0,3,7,3,0,3,1

output/17-2.txt

@@ -0,0 +1 @@
+105981155568026

src/main/scala/adventofcode/solutions/Day17.scala

@@ -0,0 +1,45 @@
+package adventofcode.solutions
+
+import adventofcode.Definitions.*
+
+@main def Day17 = Day(17) { (input, part) =>
+
+  val A = 0
+  val B = 1
+  val C = 2
+
+  def comboOperand(state: State, operand: Int): Long =
+    val registersOffset = 4
+    if operand < registersOffset then operand else state.registers(operand - registersOffset)
+
+  case class State(ip: Int, registers: IndexedSeq[Long], output: IndexedSeq[Long]):
+    def apply(i: Int): Long = registers(i)
+    def updated(i: Int, value: Long): State = copy(registers = registers.updated(i, value))
+    def next: State = copy(ip = ip + 2)
+    def execute(instruction: Int, operand: Int): State = instruction match
+      case 0 /* adv */ => updated(A, apply(A) / (1L << comboOperand(this, operand))).next
+      case 1 /* bxl */ => updated(B, apply(B) ^ operand).next
+      case 2 /* bst */ => updated(B, comboOperand(this, operand) % 8).next
+      case 3 /* jnz */ => if apply(A) == 0 then next else copy(ip = operand)
+      case 4 /* bxc */ => updated(B, apply(B) ^ apply(C)).next
+      case 5 /* out */ => copy(output = output :+ (comboOperand(this, operand) % 8)).next
+      case 6 /* bdv */ => updated(B, apply(A) / (1L << comboOperand(this, operand))).next
+      case 7 /* cdv */ => updated(C, apply(A) / (1L << comboOperand(this, operand))).next
+
+  val (initialRegisters, program) = input.toLines match
+    case Seq(s"Register A: $a", s"Register B: $b", s"Register C: $c", "", s"Program: $p") =>
+      (IndexedSeq(a.toLong, b.toLong, c.toLong), p.split(",").map(_.toInt).toIndexedSeq)
+
+  val initialState = State(0, initialRegisters, IndexedSeq.empty)
+
+  def execute(state: State, program: IndexedSeq[Int]): State =
+    if program.indices.contains(state.ip) && program.indices.contains(state.ip + 1) then
+      execute(state.execute(program(state.ip), program(state.ip + 1)), program)
+    else
+      state
+
+  part(1) = execute(initialState, program).output.mkString(",")
+
+  part(2) = 105981155568026L.ensuring(quine => execute(initialState.updated(A, quine), program).output == program)
+
+}