Array2D to Array

Question

I have Array2D of 0 and 1:

let rnd = System.Random()
let a = Array2D.init n n (fun i j  -> int(System.Math.Round(rnd.NextDouble() / index)) )

Answer 1

Here is one easy way, using the fact that [,] implements ienumerable<_>

a |> Seq.cast |> Seq.filter (fun x -> x == 1)

but if you only need the count you can do

a |> Seq.cast |> Seq.sum

as the 0 terms won't add to the sum and the terms you want to count are just 1