StoreCredit.fs

// https://code.google.com/codejam/contest/351101/dashboard#s=p0
open System.Linq

type Case = { c: int; i: int; ps: int[]; index: int[] }

let readFile filename = 
    System.IO.File.ReadLines(filename)

let transpose arr =
    let t = [|for a in [0..Array.max arr] -> -1|]
    for v in [0..arr.Length-1] do
        let m = arr.[v]
        t.[m] <- v
    t

let fileToCases (data:list<string>) = 
    let createCase sequence num  =
        let three = List.skip ((num-1) * 3) sequence |> List.take 3 |> Array.ofList
        let i = three.[1]|>int
        let bits = (three.[2] |> string).Split [|' '|] |> Array.map int
        {c=three.[0]|>int; i=i; ps=bits; index=transpose bits}
    let caseCount = List.head data |> int
    let caseData = List.tail data
    List.map (createCase caseData) [1..caseCount]
                                        
let solve (case:Case) =
    seq { 
        for i in [0..Array.length case.ps-1] do
            let value = case.ps.[i]
            if value < case.c then 
                let diff = case.c - value
                if diff < Array.length case.index && case.index.[diff] >= 0 then
                    yield (i,case.index.[diff])
    } |> Seq.head

[<EntryPoint>]
let main argv = 
    let filename = argv.[0]
    let sw = System.Diagnostics.Stopwatch.StartNew()
    let data = readFile filename |> List.ofSeq
    sw.Stop()
    printfn "io %f" sw.Elapsed.TotalMilliseconds
    let sw2 = System.Diagnostics.Stopwatch.StartNew()
    let cases = fileToCases data
    sw2.Stop()
    printfn "parse %f" sw2.Elapsed.TotalMilliseconds
    let sw3 = System.Diagnostics.Stopwatch.StartNew()
    let solutions = List.map solve cases
    sw3.Stop()
    printfn "solve %f" sw3.Elapsed.TotalMilliseconds
    printfn "%A" (solutions)
    0