Add 2024, day 3, part 2

Author: danielctull

Year2024/Sources/Day03.swift

@@ -6,22 +6,40 @@ public enum Day03: Day {
 
     public static let title = "Mull It Over"
 
-    private static let regex = Regex {
+    private static let regex1 = Regex {
         "mul("
         TryCapture.integer
         ","
         TryCapture.integer
         ")"
     }
 
+    private static let regex2 = Regex {
+        ChoiceOf {
+            regex1
+            "do()"
+            "don't()"
+        }
+    }
+
     public static func part1(_ input: Input) throws -> Int {
-        input.string.matches(of: regex).map { match in
+        input.string.matches(of: regex1).map { match in
             match.output.1 * match.output.2
         }
         .sum
     }
 
     public static func part2(_ input: Input) throws -> Int {
-        0
+        var active = true
+        var total = 0
+        for match in input.string.matches(of: regex2) {
+            switch (match.output.0, active) {
+            case ("do()", _): active = true
+            case ("don't()", _): active = false
+            case (_, false): continue
+            default: total += match.output.1! * match.output.2!
+            }
+        }
+        return total
     }
 }

Year2024/Tests/Day03Tests.swift

@@ -17,11 +17,13 @@ final class Day03Tests: XCTestCase {
     }
 
     func testPart2Examples() throws {
-        XCTAssertEqual(try Day03.part2([]), 0)
+        XCTAssertEqual(try Day03.part2([
+            "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))"
+        ]), 48)
     }
 
     func testPart2Puzzle() throws {
         let input = try Bundle.module.input(named: "Day03")
-        XCTAssertEqual(try Day03.part2(input), 0)
+        XCTAssertEqual(try Day03.part2(input), 103811193)
     }
 }