printfn "Hello World"

​

(*

        Given points in a plane (0,0), (1, 0), (0, 1), (1,1), (0, 2), (2, 2), (1, 2) - how many rectangles can be formed

*)

​

type PointsList = (int*int) list

type Point = int*int

​

let diagonals (points : PointsList) (pX, pY) : PointsList = 

    points

    |> List.filter(fun (x,y) -> (x > pX && y > pY))

let topLeft (p1X, _) (_, p2Y) = (p1X, p2Y)

let bottomRight (_, p1Y) (p2X, _) = (p2X, p1Y)

​

let numberOfRectangles (points : (int*int) list)  = 

​

    let contains (p : int*int) = points |> List.exists ((=) p)

​

    points

    |> List.collect(fun p -> diagonals points p |> List.map(fun d -> (p, d)))

    |> List.filter(fun (bL, tR) -> contains (topLeft bL tR) && contains (bottomRight bL tR))

    |> List.length

let count = 

    [

        0, 0

        1, 0

        0, 1

        1, 1

        0, 2

        2, 2

        1, 2

    ] 

    |> numberOfRectangles 

​

printfn "Hello %A" count