Advent of Code 2020 https://adventofcode.com/
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(* Common util. Should probably put this in a module or something.. *)
let get_one_line file =
try Some (input_line file) with
End_of_file -> None
let get_lines file =
let rec input lines =
match get_one_line file with
Some line -> input (line :: lines)
| None -> List.rev lines
in input []
let read_file file =
let channel = open_in(file) in
get_lines channel
let explode s = (* convert a string to a list of chars *)
let rec exp i l =
if i < 0 then l else exp (i - 1) (s.[i] :: l) in
exp (String.length s - 1) []
let implode cl = String.concat "" (List.map (String.make 1) cl)
let (<<) f g x = f(g(x)) (* how is 'compose' not in the standard library.. *)
let (>>) f g x = g(f(x))
let string_of_char = String.make 1
(* --- *)
let fix_lines glue_char lines = (* puts each group on 1 line *)
let glue s = if String.equal s "" then "\n" else glue_char in (* which char to concat the lines *)
let fix_line acc cur = acc ^ (glue cur) ^ cur in
List.fold_left fix_line "" lines
let dedup =
explode >> (* string -> char list *)
List.fold_left (fun acc x -> if String.contains acc x then acc else acc ^ (string_of_char x)) ""
let intersection group = (* find the chars common to all individuals in a group *)
List.fold_left (^) "" group (* *all* of the chars among individuals *)
|> dedup (* deduped *)
|> explode (* string to char list *)
|> List.filter (fun c -> List.for_all (fun g -> String.contains g c) group) (* check each char among each individual for membership *)
|> implode (* turn it back into a string *)
let () =
let file = read_file "day6.txt" in
let any_sum = file
|> fix_lines "" (* put each group on one line *)
|> String.split_on_char '\n' (* convert to list *)
|> List.map dedup (* remove dups *)
|> List.map String.length (* make list of lengths *)
|> List.fold_left (+) 0 (* sum list *)
in
let all_sum = file
|> fix_lines " " (* keep spaces between individuals *)
|> String.split_on_char '\n'
|> List.map String.trim
|> List.map (String.split_on_char ' ') (* each line now is a list of groups *)
|> List.map intersection (* list of strings with intersecting chars *)
|> List.map String.length (* list of lengths *)
|> List.fold_left (+) 0 (* sum list *)
in
Printf.printf "any_sum %i\n" any_sum;
Printf.printf "all_sum %i\n" all_sum;