euler-018.fs

#light

let triangle = 
    @"75
    95 64
    17 47 82
    18 35 87 10
    20 04 82 47 65
    19 01 23 75 03 34
    88 02 77 73 07 63 67
    99 65 04 28 06 16 70 92
    41 41 26 56 83 40 80 70 33
    41 48 72 33 47 32 37 16 94 29
    53 71 44 65 25 43 91 52 97 51 14
    70 11 33 28 77 73 17 78 39 68 17 57
    91 71 52 38 17 14 91 43 58 50 27 29 48
    63 66 04 68 89 53 67 30 73 16 69 87 40 31
    04 62 98 27 23 09 70 98 73 93 38 53 60 04 23" |>
    String.split(['\n']) |> 
    List.map (fun sl -> sl |> String.split([' ']) |> List.map (fun sv -> System.Int32.Parse(sv))) 

let rec selectMaxesFromPairs_aux l acc = 
    match l with
    | h0 :: h1 :: tail -> 
        let max = if h0 > h1 then h0 else h1
        selectMaxesFromPairs_aux (h1::tail) (acc @ [max])
    | _ ->
        acc
        
let selectMaxesFromPairs l = selectMaxesFromPairs_aux l []

let answer = 
    triangle |> List.reduce_right (fun l0 l1 ->
        l1 |> selectMaxesFromPairs |> List.map2 (fun v0 v1 -> v0 + v1) l0)
        
print_any answer