day10 woohooo

Author: spaenleh

README.md

@@ -17,7 +17,7 @@ Below is my current advancement in Advent of code:
 | Day 7 | :star: (45min) | :star: (33min) |
 | Day 8 | :star: (20min) | :star: (16min) |
 | Day 9 | :star: (1h51) | :star: (43min) |
-| Day 10 |  |  |
+| Day 10 | :star: (28min) | :star: (3min) |
 | Day 11 |  |  |
 | Day 12 |  |  |
 | Day 13 |  |  |

Sources/AdventOfCode.swift

@@ -11,6 +11,7 @@ let allChallenges: [any AdventDay] = [
   Day07(),
   Day08(),
   Day09(),
+  Day10(),
 ]
 
 @main

Sources/Day10.swift

@@ -0,0 +1,38 @@
+import Algorithms
+
+struct Day10: AdventDay {
+  var grid: Grid
+
+  init(data: String) {
+    grid = Grid(from: data)
+  }
+
+  func findNextStep(for startChar: String, at: Coord, summits: [Coord]) -> [Coord] {
+    var results = summits
+    if startChar == "9" {
+      results.append(at)
+      return results
+    }
+    let nextChar = String((Int(startChar) ?? 0) + 1)
+    for neighbor in at.crossNeighbors {
+      if let candidate = grid[neighbor], String(candidate) == nextChar {
+        let res = findNextStep(for: nextChar, at: neighbor, summits: summits)
+        results.append(contentsOf: res)
+      } else {
+      }
+    }
+    return results
+  }
+
+  func part1() -> Int {
+    grid.findAll(of: "0").map {
+      Set(findNextStep(for: "0", at: $0, summits: [Coord]())).count
+    }.sum
+  }
+
+  func part2() -> Int {
+    grid.findAll(of: "0").map {
+      findNextStep(for: "0", at: $0, summits: [Coord]()).count
+    }.sum
+  }
+}

Sources/Helpers/Grid.swift

@@ -11,8 +11,11 @@ struct Grid {
     raw.count
   }
 
-  subscript(_ coord: Coord) -> Element {
-    raw[coord.y][coord.x]
+  subscript(_ coord: Coord) -> Element? {
+    if coord.isInside(grid: self) {
+      return raw[coord.y][coord.x]
+    }
+    return nil
   }
 
   subscript(col: Int, row: Int) -> Element {
@@ -46,4 +49,17 @@ extension Grid {
     }
     return nil
   }
+
+  func findAll(of char: Character) -> [Coord] {
+    var coords = [Coord]()
+    for i in 0..<height {
+      for j in 0..<width {
+        let current = Coord(x: j, y: i)
+        if self[current] == char {
+          coords.append(current)
+        }
+      }
+    }
+    return coords
+  }
 }

Tests/Day10.swift

@@ -0,0 +1,54 @@
+import Testing
+
+@testable import aoc
+
+@Suite("Day10")
+struct Day10Tests {
+  let testData = """
+    89010123
+    78121874
+    87430965
+    96549874
+    45678903
+    32019012
+    01329801
+    10456732
+    """
+
+  @Test("part1")
+  func testPart1() async throws {
+    let challenge = Day10(data: testData)
+    #expect(challenge.part1() == 36)
+  }
+
+  @Test("simple")
+  func testSimple() async throws {
+    #expect(
+      Day10(
+        data: """
+          0123
+          1234
+          8765
+          9876
+          """
+      ).part1() == 1)
+    #expect(
+      Day10(
+        data: """
+          9990999
+          9991999
+          9992999
+          6543456
+          7999997
+          8599958
+          9999999
+          """
+      ).part1() == 2)
+  }
+
+  @Test("part2")
+  func testPart2() async throws {
+    let challenge = Day10(data: testData)
+    #expect(challenge.part2() == 81)
+  }
+}