Add day 4

advent-of-code/Program.fs

@@ -16,4 +16,8 @@ let main _ =
     printfn $"{day3Star1}"
     let day3Star2 = day_3.Star2.main
     printfn $"{day3Star2}"
+    let day4Star1 = day_4.Star1.main
+    printfn $"{day4Star1}"
+    let day4Star2 = day_4.Star2.main
+    printfn $"{day4Star2}"
     0

advent-of-code/tasks/day-4/Star1.fs

@@ -0,0 +1,37 @@
+module advent_of_code.tasks.day_4.Star1
+
+open System
+open System.IO
+
+let stream = new StreamReader("tasks/day-4/input.txt")
+
+let getPos (grid: string list) (pos: int * int) =
+    let y, x = pos.Deconstruct()
+    if (y < 0 || y >= grid.Length || x < 0 || x >= grid[y].Length) then
+        0
+    else
+        if grid[y][x] = '@' then 1 else 0
+
+let isMovable (grid: string list) (y: int) (x: int) =
+    if (grid[y][x] = '.') then
+        false
+    else
+        let posList = [
+            (y - 1, x - 1); (y - 1, x); (y - 1, x + 1)
+            (y, x - 1); (y, x + 1)
+            (y + 1, x - 1); (y + 1, x); (y + 1, x + 1)
+        ]
+        let adjacentList = posList |> List.map (getPos grid)
+        List.sum adjacentList < 4
+
+let rec countRow (grid: string list) (y: int) (x: int) =
+    if x = grid[y].Length then 0 else
+    (if (isMovable grid y x) then 1 else 0) + (countRow grid y (x + 1))
+
+let rec countGrid (grid: string list) (y: int) =
+    if y = grid.Length then 0 else
+    (countRow grid y 0) + (countGrid grid (y + 1))
+
+let main =
+    let grid = stream.ReadToEnd().Split('\n') |> Array.toList
+    countGrid grid 0

advent-of-code/tasks/day-4/Star2.fs

@@ -0,0 +1,46 @@
+module advent_of_code.tasks.day_4.Star2
+
+open System
+open System.IO
+
+let stream = new StreamReader("tasks/day-4/input.txt")
+
+let mutable removed = Set.empty
+
+let getPos (grid: string list) (pos: int * int) =
+    let y, x = pos.Deconstruct()
+    if (y < 0 || y >= grid.Length || x < 0 || x >= grid[y].Length || removed.Contains((y, x))) then
+        0
+    else
+        if grid[y][x] = '@' then 1 else 0
+
+let isMovable (grid: string list) (y: int) (x: int) =
+    if (grid[y][x] = '.' || removed.Contains((y, x))) then
+        false
+    else
+        let posList = [
+            (y - 1, x - 1); (y - 1, x); (y - 1, x + 1)
+            (y, x - 1); (y, x + 1)
+            (y + 1, x - 1); (y + 1, x); (y + 1, x + 1)
+        ]
+        let adjacentList = posList |> List.map (getPos grid)
+        if (List.sum adjacentList < 4) then
+            removed <- removed.Add((y, x))
+            true
+        else false
+
+let rec countRow (grid: string list) (y: int) (x: int) =
+    if x = grid[y].Length then 0 else
+    (if (isMovable grid y x) then 1 else 0) + (countRow grid y (x + 1))
+
+let rec countGrid (grid: string list) (y: int) =
+    if y = grid.Length then 0 else
+    (countRow grid y 0) + (countGrid grid (y + 1))
+
+let rec loop (grid: string list) =
+    let removables = countGrid grid 0
+    if removables = 0 then 0 else removables + loop grid
+
+let main =
+    let grid = stream.ReadToEnd().Split('\n') |> Array.toList
+    loop grid