day4 gleam

day4/day4.gleam

···
+import gleam/bool
+import gleam/dict
+import gleam/int
+import gleam/io
+import gleam/list
+import gleam/string
+import simplifile
+
+pub fn main() {
+  let assert Ok(raw_input) = simplifile.read("src/day4/input.txt")
+
+  let input =
+    raw_input
+    |> string.trim
+    |> string.split("\n")
+    |> list.index_map(fn(x, i) {
+      string.to_graphemes(x)
+      |> list.index_map(fn(y, ii) { #(#(ii, i), y) })
+    })
+    |> list.flatten
+    |> dict.from_list
+
+  let part1 =
+    dict.fold(input, 0, fn(acc, k, v) {
+      use <- bool.guard(v == ".", acc)
+      let n =
+        list.flat_map([-1, 0, 1], fn(x) {
+          list.map([-1, 0, 1], fn(y) { #(k.0 + x, k.1 + y) })
+        })
+        |> list.filter(fn(x) { x != k })
+        |> list.fold(0, fn(acc2, k2) {
+          case dict.get(input, k2) {
+            Ok("@") -> acc2 + 1
+            _ -> acc2
+          }
+        })
+      case n < 4 {
+        True -> acc + 1
+        False -> acc
+      }
+    })
+
+  io.println("Part 1: " <> int.to_string(part1))
+
+  let part2 = do_remove(input, 0)
+
+  io.println("Part 2: " <> int.to_string(part2))
+}
+
+fn do_remove(rolls: dict.Dict(#(Int, Int), String), count: Int) -> Int {
+  let #(c, r) =
+    dict.fold(rolls, #(0, []), fn(acc, k, v) {
+      use <- bool.guard(v == ".", acc)
+      let n =
+        list.flat_map([-1, 0, 1], fn(x) {
+          list.map([-1, 0, 1], fn(y) { #(k.0 + x, k.1 + y) })
+        })
+        |> list.filter(fn(x) { x != k })
+        |> list.fold(0, fn(acc2, k2) {
+          case dict.get(rolls, k2) {
+            Ok("@") -> acc2 + 1
+            _ -> acc2
+          }
+        })
+      case n < 4 {
+        True -> #(acc.0 + 1, [#(k, "."), ..acc.1])
+        False -> #(acc.0, [#(k, v), ..acc.1])
+      }
+    })
+  case c == 0 {
+    True -> count
+    False -> do_remove(dict.from_list(r), count + c)
+  }
+}