day5 done

Author: spaenleh

README.md

@@ -12,7 +12,7 @@ Below is my current advancement in Advent of code:
 | Day 2 | :star: | :star: |
 | Day 3 | :star: | :star: |
 | Day 4 | :star: | :star: |
-| Day 5 | :star: (22min) |  |
+| Day 5 | :star: (22min) | :star: (21min) |
 | Day 6 |  |  |
 | Day 7 |  |  |
 | Day 8 |  |  |

Sources/Day05.swift

@@ -1,22 +1,13 @@
 import Algorithms
 
-struct Rule {
-  var before: Int
-  var after: Int
-
-}
-extension Rule {
-  init(data: Substring) {
-    let parts = data.split(separator: "|")
-    before = Int(parts[0]) ?? 0
-    after = Int(parts[1]) ?? 0
-  }
-}
-
 struct Day05: AdventDay {
   var rules: [Int: [Int]]
   var updates: [[Int]]
 
+  func middlePage(_ update: [Int]) -> Int {
+    update[update.count / 2]
+  }
+
   init(data: String) {
     let parts = data.split(separator: "\n\n")
     rules = [Int: [Int]]()
@@ -29,22 +20,44 @@ struct Day05: AdventDay {
     updates = parts[1].lines().map { $0.integers(separator: ",") }
   }
 
+  func isCorrect(_ update: [Int]) -> Bool {
+    for (idx, page) in update.enumerated() {
+      let rulesForPage = rules[page, default: [Int]()]
+      let brokenRules = rulesForPage.map { update[idx + 1..<update.count].contains($0) }.count {
+        $0 == true
+      }
+      if brokenRules > 0 {
+        return false
+      }
+    }
+    return true
+  }
+
   func part1() -> Int {
-    updates.filter { update in
-      for (idx, page) in update.enumerated() {
-        let rulesForPage = rules[page, default: [Int]()]
-        let brokenRules = rulesForPage.map { update[idx + 1..<update.count].contains($0) }.count {
-          $0 == true
-        }
-        if brokenRules > 0 {
-          return false
+    updates.filter { isCorrect($0) }.map { middlePage($0) }.sum
+  }
+
+  func fixOrder(_ update: [Int]) -> [Int] {
+    var fixedUpdate = update
+    for (idx, page) in update.enumerated() {
+      let rulesForPage = rules[page, default: [Int]()]
+      let brokenRules = rulesForPage.map { update[idx + 1..<update.count].contains($0) }
+      for (isBroken, infringingPage) in zip(brokenRules, rulesForPage) {
+        if isBroken {
+          if let infringingIndex = fixedUpdate.firstIndex(of: infringingPage) {
+            let value = fixedUpdate.remove(at: infringingIndex)
+            fixedUpdate.insert(value, at: idx)
+          }
         }
       }
-      return true
-    }.map { update in update[update.count / 2] }.sum
+    }
+    if !isCorrect(fixedUpdate) {
+      fixedUpdate = fixOrder(fixedUpdate)
+    }
+    return fixedUpdate
   }
 
   func part2() -> Int {
-    0
+    updates.filter { !isCorrect($0) }.map { middlePage(fixOrder($0)) }.sum
   }
 }

Tests/Day04.swift

@@ -27,7 +27,7 @@ struct Day04Tests {
         XMAS
         """)
     #expect(
-      searchInNeighbors(pos: Coord(x: 0, y: 0), grid) == [Coord(x: 1, y: 0), Coord(x: 1, y: 1)])
+      searchInNeighbors(pos: Coord(x: 0, y: 0), grid) == [Coord(x: 1, y: 1), Coord(x: 1, y: 0)])
   }
 
   @Test("part1 simple")
@@ -39,7 +39,7 @@ struct Day04Tests {
       XMAS
       """
     let challenge = Day04(data: grid)
-    #expect(challenge.part1() == 2)
+    #expect(challenge.part1() == 6)
   }
 
   @Test("part1")

Tests/Day05.swift

@@ -50,6 +50,9 @@ struct Day05Tests {
   @Test("part2")
   func testPart2() async throws {
     let challenge = Day05(data: testData)
-    #expect(challenge.part2() == 0)
+    #expect(challenge.fixOrder([75, 97, 47, 61, 53]) == [97, 75, 47, 61, 53])
+    #expect(challenge.fixOrder([61, 13, 29]) == [61, 29, 13])
+    #expect(challenge.fixOrder([97, 13, 75, 29, 47]) == [97, 75, 47, 29, 13])
+    #expect(challenge.part2() == 123)
   }
 }