There was a long delay on this one due to Christmas, and a vacation in between, so I definitely missed my goal of 25 languages in 25 days.  But let’s see how far I can go.

Part 2

Part 2 is much tougher.  Instead of finding the first non-blacklisted IPs, we needed a count of all non-blacklisted IPs.

The basic idea was to start at zero, and then find the first number that is not in a blacklisted range.  Then find the next number that is a range and subtract the difference.  Add that difference to the sum, and start again with the ranges that are left.

First, I had to implement a solve method to do the basic checking

let rec solve num accum  ranges = 
        let matching = (getFiltersMatching num ranges)
        let remainingRanges = (getRemainingRanges ranges num)
        match Seq.isEmpty matching with
        | true ->
            match (Seq.isEmpty remainingRanges) with
            | true -> accum + (System.UInt32.MaxValue - num) + 1u
            | false -> 
                let invalidNumber = (getFirstInvalidNumber remainingRanges)
                let diff = invalidNumber - num
                solve (getNextStartingNumber (invalidNumber+1u) remainingRanges) (accum + diff) remainingRanges
        | false ->     
            let lastValid = (getLastValidNumber matching)
            match lastValid with
            | System.UInt32.MaxValue -> accum
            | otherwise -> solve (lastValid+1u) accum remainingRanges
       

[]
let main argv = 
        Seq.toArray readlines 
        |> Seq.map (fun x -> x.Split[|'-'|])
        |> Seq.map toInts
        |> solve 0u 0u
        |> printfn "%d"
        0

This was ugly code, to be sure.  First I check if I’m already in a range, and if I am, either I’m at the end of my int range, or I need to recursively check the number out of my current range.  If I’m currently in a number not in a range, I need to check what the next invalid number is.  I subtract my current number from the invalid number and then add it to an accumulator.

I had to write a few utility functions to find information about the ranges

let getFirstInvalidNumber ranges =
         ranges
         |> Seq.map (fun r -> (Seq.head r))
         |> Seq.min

let getNextStartingNumber num ranges = 
        getFiltersMatching num ranges
        |> Seq.map (fun r -> (Seq.last r))
        |> Seq.filter (fun x -> x >= num)
        |> Seq.min

let isNumBeforeRange num range =
        num  Seq.filter (fun r -> (isNumBeforeRange num r) )

let getLastValidNumber ranges =
         match (Seq.isEmpty ranges) with
         | false ->
                ranges
                |> Seq.map (fun r -> (Seq.last r))
                |> Seq.max
         | true -> System.UInt32.MaxValue

These were just straight forward sequence operations.

 

Wrap-up

F# did not go as smoothly as I wanted.  I got part two wrong at first, and it took me a while to write ugly code.  The documentation was great though, and Visual Studio Code was a blast to write F# in (inline type annotations? Yes, please.)  I would definitely consider F# for a .NET project over OcaML.

I give myself a C+ on this one.  I had a vacation in the middle, but I still had some time on either end that I was working on this one.

Next up, PHP.