Day 17 part 1

2024/src/main/kotlin/day17.kt

@@ -0,0 +1,51 @@
+/*
+Register A: 21539243
+Register B: 0
+Register C: 0
+
+Program: 2,4,1,3,7,5,1,5,0,3,4,1,5,5,3,0
+ */
+
+class Computer(var a: Int = 0, var b: Int = 0, var c: Int = 0, var ip: Int = 0, val memory: List<Int>) {
+    val output = mutableListOf<Int>()
+
+    fun run(): List<Int> {
+        ip = 0
+        output.clear()
+
+        while (0 <= ip && (ip + 1) < memory.size) {
+            when (memory[ip]) {
+                0 -> a /= (1 shl comboOperand())
+                1 -> b = b xor literalOperand()
+                2 -> b = comboOperand() and 7
+                3 -> if (a != 0) {
+                    ip = literalOperand() - 2
+                }
+                4 -> b = b xor c
+                5 -> output.add(comboOperand() and 7)
+                6 -> b = a / (1 shl comboOperand())
+                7 -> c = a / (1 shl comboOperand())
+                else -> error("Invalid opcode ${memory[ip]}")
+            }
+            ip += 2
+        }
+        return output.toList()
+    }
+
+    private fun comboOperand(): Int = when(val value = memory[ip + 1]) {
+        0, 1, 2, 3 -> value
+        4 -> a
+        5 -> b
+        6 -> c
+        else -> error("Invalid combo operand $value")
+    }
+
+    private fun literalOperand(): Int = memory[ip + 1]
+
+}
+
+fun main() {
+    val computer = Computer(a = 21539243, memory = listOf(2,4,1,3,7,5,1,5,0,3,4,1,5,5,3,0))
+    val output = computer.run().joinToString(separator = ",")
+    println("Part 1: $output")
+}