aoc2022/day6.m

:- module day6.
:- interface.
:- import_module basics.

:- pred run(part::in, lines::in, answer::out) is cc_multi.

:- implementation.
:- import_module int.
:- import_module string.
:- import_module list.

:- pred all_diff(list(T)::in) is semidet.
all_diff([]).
all_diff([X | Xs]) :- not member(X, Xs), all_diff(Xs).

:- pred window(int::in, list(T)::in, int::out, list(T)::out) is nondet.
window(Len, In,     0,     Out) :- take(Len, In, Out).
window(Len, [_|In], I + 1, Out) :- window(Len, In, I, Out).

:- pred start_index(int::in, list(T)::in, int::out) is cc_nondet.
start_index(Len, Input, Index) :- window(Len, Input, Index, Out), all_diff(Out).

:- func length(part) = int.
length(one) = 4.
length(two) = 14.

:- pragma no_determinism_warning(run/3).
run(Part, Lines, int(Out)) :-
  if Lines = [Line] then
    Len = length(Part),
    (if start_index(Len, to_char_list(Line), Out0)
     then Out = Len + Out0
     else die("not found"))
  else die("bad input").