Add 2024, day 2, part 1

danielctull · Dec 2, 2024 · 12c4f29 · 12c4f29
1 parent 2f7958b
commit 12c4f29
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Showing 2 changed files with 33 additions and 8 deletions.
diff --git a/Year2024/Sources/Day02.swift b/Year2024/Sources/Day02.swift
@@ -11,15 +11,32 @@ public enum Day02: Day {
                 .split(whereSeparator:(\.isWhitespace))
                 .map(Int.init)
 
-            let differences = zip(values, values.dropFirst())
-                .map(-)
-
-            return differences.map(abs).allSatisfy { $0 < 4 }
-                && differences.map(\.signum).allSame
+            return check(differences(values))
         }
     }
 
     public static func part2(_ input: Input) throws -> Int {
-        0
+        try input.lines.count {
+            let values = try $0
+                .split(whereSeparator:(\.isWhitespace))
+                .map(Int.init)
+
+            if check(differences(values)) { return true }
+
+            return (0..<values.count).contains { index in
+                var new = values
+                new.remove(at: index)
+                return check(differences(new))
+            }
+        }
     }
 }
+
+fileprivate func differences(_ values: [Int]) -> [Int] {
+    zip(values.dropFirst(), values).map(-)
+}
+
+fileprivate func check(_ differences: [Int]) -> Bool {
+    differences.map(abs).allSatisfy { 0 < $0 && $0 < 4 }
+        && differences.map(\.signum).allSame
+}
diff --git a/Year2024/Tests/Day02Tests.swift b/Year2024/Tests/Day02Tests.swift
@@ -22,11 +22,19 @@ final class Day02Tests: XCTestCase {
     }
 
     func testPart2Examples() throws {
-        XCTAssertEqual(try Day02.part2([]), 0)
+        XCTAssertEqual(try Day02.part2([
+            "7 6 4 2 1",
+            "1 2 7 8 9",
+            "9 7 6 2 1",
+            "1 3 2 4 5",
+            "8 6 4 4 1",
+            "1 3 6 7 9",
+          ]), 4)
+
     }
 
     func testPart2Puzzle() throws {
         let input = try Bundle.module.input(named: "Day02")
-        XCTAssertEqual(try Day02.part2(input), 0)
+        XCTAssertEqual(try Day02.part2(input), 354)
     }
 }