day(03): refactor

Signed-off-by: Matej Focko <me@mfocko.xyz>

src/Day03.kt

@@ -13,26 +13,12 @@ class Day03(
     )
 
     companion object {
-        private val MUL_REGEX = "mul\\((\\d+),(\\d+)\\)".toRegex()
         private val OP_REGEX = "(mul\\((\\d+),(\\d+)\\)|do\\(\\)|don't\\(\\))".toRegex()
     }
 
-    private val memory: String = readInputAsString(3, inputType)
-    private var multiplications: List<Pair<Int, Int>> = listOf()
-    private var allInstructions: List<Instruction> = listOf()
-
-    override fun precompute() {
-        multiplications =
-            MUL_REGEX
-                .findAll(memory)
-                .map {
-                    val (x, y) = it.destructured
-                    x.toInt() to y.toInt()
-                }.toList()
-
-        allInstructions =
+    private val instructions: List<Instruction> =
         OP_REGEX
-                .findAll(memory)
+            .findAll(readInputAsString(3, inputType))
             .map {
                 val (op, l, r) = it.destructured
 
@@ -51,12 +37,20 @@ class Day03(
 
                 Instruction(type, value)
             }.toList()
+
+    override fun precompute() { // no-op
     }
 
-    override fun part1(): Int = multiplications.sumOf { it.first * it.second }
+    override fun part1(): Int =
+        instructions.sumOf {
+            when (it.type) {
+                InstructionType.Mul -> it.value
+                else -> 0
+            }
+        }
 
     override fun part2(): Int =
-        allInstructions
+        instructions
             .fold(true to 0) { (running, sum), instr ->
                 var (running, sum) = running to sum
                 when (instr.type) {