Day 4: part 1 WIP

Author: horothesun

src/main/scala/Day04.scala

@@ -3,20 +3,25 @@ import cats.syntax.all.*
 
 object Day04:
 
-//  val s: Store[Int, Option[Char]] = Store(f = _ => Some('a'), s = 0)
-//  val x: Option[Char] = s.peeks(identity)
-//  val y: List[Option[Char]] = s.experiment[List](n => List.range(start = n, end = n + 3))
+  case class Word(s: String):
+    val length: Int = s.length
+    val toOptionChars: List[Option[Char]] = s.toList.map(Some.apply)
 
   case class Pos(row: Int, col: Int)
 
   object Pos:
     val zero = Pos(row = 0, col = 0)
 
+  type StoreGrid = Store[Pos, Option[Char]]
+
+  enum WordCheckResult:
+    case Found, NotFound
+
   case class Grid(rows: List[List[Char]]):
 
-    private val toVectors: Vector[Vector[Char]] = rows.map(_.toVector).toVector
+    val toVectors: Vector[Vector[Char]] = rows.map(_.toVector).toVector
 
-    def toStore: Store[Pos, Option[Char]] = Store(
+    def toStore: StoreGrid = Store(
       p => toVectors.get(p.row).flatMap(_.get(p.col)),
       s = Pos.zero
     )
@@ -25,4 +30,41 @@ object Day04:
       rows.zipWithIndex.flatMap((row, rowIndex) => row.zipWithIndex.map((_, colIndex) => Pos(rowIndex, colIndex)))
 
   object Grid:
+
     def parse(rows: List[String]): Option[Grid] = Grid(rows = rows.map(_.toList)).some
+
+    /*
+      XMAS
+      ....
+      ....
+      ....
+     */
+    def topLeftPositions(w: Word)(p: Pos): List[Pos] =
+      List.range(start = p.col, end = p.col + w.length).map(col => Pos(p.row, col))
+
+    def wordCheckTopLeft(w: Word, store: StoreGrid): WordCheckResult = wordCheck(topLeftPositions, w, store)
+
+    /*
+      ...S
+      ..A.
+      .M..
+      X...
+     */
+    def ascDiagonalPositions(w: Word)(p: Pos): List[Pos] =
+      List.range(start = 0, end = w.length).reverse.map(i => Pos(row = i + p.row, col = w.length - i - 1 + p.col))
+
+    def wordCheckAscDiagonal(w: Word, store: StoreGrid): WordCheckResult = wordCheck(ascDiagonalPositions, w, store)
+
+    /*
+      X...
+      .M..
+      ..A.
+      ...S
+     */
+    def descDiagonalPositions(w: Word)(p: Pos): List[Pos] =
+      List.range(start = 0, end = w.length).map(i => Pos(row = i + p.row, col = i + p.col))
+
+    def wordCheckDescDiagonal(w: Word, store: StoreGrid): WordCheckResult = wordCheck(descDiagonalPositions, w, store)
+
+    def wordCheck(positions: Word => Pos => List[Pos], w: Word, store: StoreGrid): WordCheckResult =
+      if w.toOptionChars == store.experiment(positions(w)) then WordCheckResult.Found else WordCheckResult.NotFound

src/test/scala/Day04Suite.scala

@@ -16,7 +16,7 @@ class Day04Suite extends ScalaCheckSuite:
   test("big input parsed to something"):
     assert(Grid.parse(rows = bigInput).isDefined)
 
-  test("Grid.allPositions example"):
+  test("Grid allPositions example"):
     assertEquals(
       Grid(rows = List(List('a', 'b', 'c'), List('d', 'e', 'f'))).allPositions,
       List(
@@ -32,6 +32,36 @@ class Day04Suite extends ScalaCheckSuite:
   property("Grid |allPositions| = rows * columns"):
     forAll(nonEmptyGridGen)(neg => assertEquals(neg.allPositions.length, neg.rows.length * neg.rows.head.length))
 
+  test("topLeftPositions example"):
+    assertEquals(
+      Grid.topLeftPositions(Word("XYZ"))(Pos(row = 2, col = 4)),
+      List(
+        Pos(row = 2, col = 4),
+        Pos(row = 2, col = 5),
+        Pos(row = 2, col = 6)
+      )
+    )
+
+  test("ascDiagonalPositions example"):
+    assertEquals(
+      Grid.ascDiagonalPositions(Word("XYZ"))(Pos(row = 2, col = 4)),
+      List(
+        Pos(row = 4, col = 4),
+        Pos(row = 3, col = 5),
+        Pos(row = 2, col = 6)
+      )
+    )
+
+  test("descDiagonalPositions example"):
+    assertEquals(
+      Grid.descDiagonalPositions(Word("XYZ"))(Pos(row = 2, col = 4)),
+      List(
+        Pos(row = 2, col = 4),
+        Pos(row = 3, col = 5),
+        Pos(row = 4, col = 6)
+      )
+    )
+
 object Day04Suite:
 
   val bigInput: List[String] = getLinesFromFile("src/test/scala/day04_input.txt")