Completed Day 25 Part 1

Sources/AdventOfCode.swift

@@ -26,7 +26,8 @@ let allChallenges: [any AdventDay] = [
   Day21(), 
   Day22(), 
   Day23(), 
-  Day24()
+  Day24(), 
+  Day25()
 ]
 
 @main

Sources/Day25.swift

@@ -0,0 +1,80 @@
+import Algorithms
+
+struct Day25: AdventDay {
+  var data: String
+
+  struct Combination: Hashable {
+    let isLock: Bool
+
+    let col1: UInt8
+    let col2: UInt8
+    let col3: UInt8
+    let col4: UInt8
+    let col5: UInt8
+
+    init(fromData input: some StringProtocol) {
+      self.isLock = input.first! == "#"
+
+      var col1: UInt8?
+      var col2: UInt8?
+      var col3: UInt8?
+      var col4: UInt8?
+      var col5: UInt8?
+
+      for (lineNum, line) in input.split(separator: "\n").enumerated() {
+        assert(line.count == 5, "Got malformed line \(line)")
+
+        if self.isLock {
+          if col1 == nil, line[line.index(line.startIndex, offsetBy: 0)] == "." { col1 = UInt8(lineNum - 1) }
+          if col2 == nil, line[line.index(line.startIndex, offsetBy: 1)] == "." { col2 = UInt8(lineNum - 1) }
+          if col3 == nil, line[line.index(line.startIndex, offsetBy: 2)] == "." { col3 = UInt8(lineNum - 1) }
+          if col4 == nil, line[line.index(line.startIndex, offsetBy: 3)] == "." { col4 = UInt8(lineNum - 1) }
+          if col5 == nil, line[line.index(line.startIndex, offsetBy: 4)] == "." { col5 = UInt8(lineNum - 1) }
+        } else {
+          if col1 == nil, line[line.index(line.startIndex, offsetBy: 0)] == "#" { col1 = UInt8(6 - lineNum) }
+          if col2 == nil, line[line.index(line.startIndex, offsetBy: 1)] == "#" { col2 = UInt8(6 - lineNum) }
+          if col3 == nil, line[line.index(line.startIndex, offsetBy: 2)] == "#" { col3 = UInt8(6 - lineNum) }
+          if col4 == nil, line[line.index(line.startIndex, offsetBy: 3)] == "#" { col4 = UInt8(6 - lineNum) }
+          if col5 == nil, line[line.index(line.startIndex, offsetBy: 4)] == "#" { col5 = UInt8(6 - lineNum) }
+        }
+      }
+
+      self.col1 = col1!
+      self.col2 = col2!
+      self.col3 = col3!
+      self.col4 = col4!
+      self.col5 = col5!
+    }
+
+    func fits(_ other: Combination) -> Bool {
+      assert(self.isLock != other.isLock)
+
+      return self.col1 + other.col1 <= 5
+          && self.col2 + other.col2 <= 5
+          && self.col3 + other.col3 <= 5
+          && self.col4 + other.col4 <= 5
+          && self.col5 + other.col5 <= 5
+    }
+  }
+
+  func part1() -> Any {
+    let combinations = Set(data.split(separator: "\n\n").map(Combination.init))
+
+    let locks = combinations.filter(\.isLock)
+    let keys = combinations.subtracting(locks)
+
+    var count = 0
+
+    for key in keys {
+      for lock in locks {
+        if key.fits(lock) { count += 1 }
+      }
+    }
+
+    return count
+  }
+
+  func part2() -> Any {
+    return 0
+  }
+}

Tests/Day25.swift

@@ -0,0 +1,57 @@
+import Testing
+
+@testable import AdventOfCode
+
+struct Day25Tests {
+
+  let testData = """
+  #####
+  .####
+  .####
+  .####
+  .#.#.
+  .#...
+  .....
+
+  #####
+  ##.##
+  .#.##
+  ...##
+  ...#.
+  ...#.
+  .....
+
+  .....
+  #....
+  #....
+  #...#
+  #.#.#
+  #.###
+  #####
+
+  .....
+  .....
+  #.#..
+  ###..
+  ###.#
+  ###.#
+  #####
+
+  .....
+  .....
+  .....
+  #....
+  #.#..
+  #.#.#
+  #####
+  
+  """
+
+  @Test func testPart1() async throws {
+    #expect(String(describing: Day25(data: testData).part1()) == "3")
+  }
+
+  @Test func testPart2() async throws {
+    #expect(true)
+  }
+}