Advent of Code 2016 Day 3

day3.fs

let isTriangle (x,y,z) = 
    x + y > z &&
    x + z > y &&
    y + z > x

let lineTo3Ints (line: string) = 
    let chunks = line.Split( [|" "|], StringSplitOptions.RemoveEmptyEntries )
    if (Seq.length chunks) <> 3 then None
    else
        let values = chunks |> Seq.map System.Int32.Parse
        Some values

let tuple3 values = 
    let a = Seq.toArray values
    (a.[0],a.[1],a.[2])

let lineToNumbers line = 
    let numbers = lineTo3Ints line
    match numbers with
    | Some values -> Seq.toList values
    | None -> []    

let leftToRightSequence lines =         
    Seq.fold (fun values line -> values @ (lineToNumbers line)) [] lines

let every start skip numbers = 
  numbers |> List.mapi (fun i el -> el, i)              
      |> List.filter (fun (_, i) -> ((i - start) % skip) = 0) 
      |> List.map fst 

let topTopBottom lines = 
    let numbers = leftToRightSequence lines
    (every 0 3 numbers) @ (every 1 3 numbers) @ (every 2 3 numbers)


let rec chunks chunkSize acc numbers = 
    if List.length numbers < chunkSize then acc
    else chunks chunkSize (acc @ [List.take chunkSize numbers]) (List.skip chunkSize numbers)
        
let findTriangles numbers = 
    let threes = chunks 3 [] numbers;            
    List.filter (fun chunk -> isTriangle (tuple3 chunk)) threes

let day3 = 
    printfn "\n\nDay 3\n"    
    let seperators = [|"\n";"\r"|]
    let lines = input.Split( seperators, StringSplitOptions.RemoveEmptyEntries )    
    
    let numbers = leftToRightSequence lines    
    let triangles = findTriangles numbers
                   
    printfn "Part 1: %d" (Seq.length triangles)
    
    let numbers = topTopBottom lines       
    let triangles = findTriangles numbers

    printfn "Part 2: %d" (Seq.length triangles)