1 files changed, 58 insertions, 0 deletions
diff --git a/day1.fsx b/day1.fsx
new file mode 100644
index 0000000..cec57b5
--- /dev/null
+++ b/day1.fsx
@@ -0,0 +1,58 @@
+open System.IO
+
+let lines = (File.ReadAllText "day1.txt").Split ", "
+
+let rec move (steps: string[]) (dir: int) (x: int) (y: int): int =
+    if (Array.length steps) = 0 then abs x + abs y
+    else
+        let instDir = steps[0][0]
+        let instLen = steps[0][1..] |> int
+        let newDir =
+            match instDir with
+            | 'R' -> (dir + 1) % 4
+            | 'L' -> (((dir - 1) % 4) + 4) % 4
+            | _ -> -500 // will never get to this point but the compiler yells at me otherwise
+        
+        let (newX, newY) =
+            match newDir with
+            | 0 -> (x, y + instLen)
+            | 1 -> (x + instLen, y)
+            | 2 -> (x, y - instLen)
+            | 3 -> (x - instLen, y)
+            | _ -> (-500, -500) // again will never reach here
+        move steps[1..] newDir newX newY
+
+let rec move2 (steps: string[]) (dir: int) (x: int) (y: int) (visited: Set<int * int>): int =
+    let instDir = steps[0][0]
+    let instLen = steps[0][1..] |> int
+    let newDir = 
+        match instDir with 
+        | 'R' -> (dir + 1) % 4
+        | 'L' -> (((dir - 1) % 4) + 4) % 4
+        | _ -> -500
+    
+    let newVisited =
+        match newDir with
+        | 0 -> set [for newY in seq {y+1 .. y+instLen} do yield (x, newY)]
+        | 1 -> set [for newX in seq {x+1 .. x+instLen} do yield (newX, y)]
+        | 2 -> set [for newY in seq {y-1 .. -1 .. y-instLen} do yield (x, newY)]
+        | 3 -> set [for newX in seq {x-1 .. -1 .. x-instLen} do yield (newX, y)]
+        | _ -> Set.empty
+    
+    let diff = Set.intersect visited newVisited
+    if (Set.count diff) > 0 then
+        let pointList = [for point in diff do yield point]
+        let (pointX, pointY) = pointList[0] // assume there is only one intersection at a time
+        abs pointX + abs pointY
+    else
+        let (newX, newY) =
+            match newDir with
+            | 0 -> (x, y + instLen)
+            | 1 -> (x + instLen, y)
+            | 2 -> (x, y - instLen)
+            | 3 -> (x - instLen, y)
+            | _ -> (-500, -500)
+        move2 steps[1..] newDir newX newY (Set.union visited newVisited)
+
+move lines 0 0 0 |> printfn "%A" 
+move2 lines 0 0 0 Set.empty |> printfn "%A"