Day 04

src/day04.scala

@@ -0,0 +1,62 @@
+package aoc
+package day04
+
+val dayNumber = "04"
+
+@main def part1: Unit =
+  println(part1(loadInput(dayNumber)))
+
+@main def part2: Unit =
+  println(part2(loadInput(dayNumber)))
+
+def part1(input: String): String =
+  val grid = input.split("\n")
+  val coords =
+    for
+      y <- 0 until grid.length
+      x <- 0 until grid.head.length
+    yield (x, y) -> grid(y)(x)
+  val lettersMap = coords.toMap
+  val xs = coords.collect { case (x, y) -> 'X' => (x, y) }
+
+  val offsets = (
+    for
+      ox <- -1 to 1
+      oy <- -1 to 1
+      if !(ox == 0 && oy == 0)
+    yield (ox, oy)
+  ).map((ox, oy) => List.iterate((0, 0), 4)((x, y) => (x + ox, y + oy)))
+
+  xs.map((x, y) =>
+    offsets
+      .map(_.flatMap((ox, oy) => lettersMap.get((x + ox, y + oy))))
+      .count(_ == List('X', 'M', 'A', 'S'))
+  ).sum
+    .toString
+
+def part2(input: String): String =
+  val grid = input.split("\n")
+  val coords =
+    for
+      y <- 0 until grid.length
+      x <- 0 until grid.head.length
+    yield (x, y) -> grid(y)(x)
+  val lettersMap = coords.toMap
+  val as = coords.collect { case (x, y) -> 'A' => (x, y) }
+
+  val offsets = List(
+    (-1 -> -1, 1 -> 1),
+    (-1 -> 1, 1 -> -1)
+  ).flatMap((a, b) =>
+    List(
+      List(a, 0 -> 0, b),
+      List(b, 0 -> 0, a)
+    )
+  )
+
+  as.map((x, y) =>
+    offsets
+      .map(_.flatMap((ox, oy) => lettersMap.get((x + ox, y + oy))))
+      .count(_ == List('M', 'A', 'S'))
+  ).count(_ == 2)
+    .toString