blob: dd9916a61f6e616b755be84dfff6098743189691 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
open System.IO
open System.Text.RegularExpressions
open System
let lines = File.ReadLines "day4.txt" |> Seq.toList
let (|Regex|_|) pattern input =
let m = Regex.Match(input, pattern)
if m.Success then Some(List.tail [for g in m.Groups -> g.Value])
else None
let validChecksum (info: string * int * string) =
let (name, idNum, checksum) = info
let counts =
name
|> String.filter ((<>) '-')
|> Seq.toList
|> List.countBy id
|> List.sortBy fst
|> List.sortBy (snd >> fun x -> -x)
let topFive = (List.map fst counts)[0..4] |> Seq.map string|> String.concat ""
if topFive = checksum then idNum else 0
let getInfo string =
match string with
| Regex "([a-z\-]*)-(\d+)\[([a-z]{5})\]" [name; id; checksum] ->
(name, int id, checksum)
| _ -> ("", 0, "")
let totalChecksum =
List.map (getInfo >> validChecksum) >> List.sum
// part 1
totalChecksum lines |> printfn "%A"
// part 2
let decrypt (offset: int) (letter: char) : string =
match letter with
| '-' -> " "
| _ ->
int letter
|> fun x -> x - (int 'a') + offset
|> fun x -> x % 26
|> ((+) (int 'a'))
|> Convert.ToChar
|> string
let decryptValid (info: string * int * string) =
let (name, idNum, checksum) = info
Seq.toList name |> List.map (decrypt idNum) |> String.concat "", idNum
let decrypted =
List.map (getInfo >> decryptValid) >> List.filter (fst >> fun x -> x.Contains "north")
decrypted lines |> printfn "%A"
|