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make part2 clearer

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Dory 2023-12-04 09:21:56 -08:00
parent 26365275e8
commit 0378b27aed
1 changed files with 19 additions and 21 deletions
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04/part2.pl
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@ -1,27 +1,6 @@
:- table match/3.
:- table sum/5.
% match1(WinningNums, CardNums, NMatches)
match1(_, [], 0).
match1(Wins, [X|Nums], N) :- member(X, Wins), match1(Wins, Nums, N1), N is N1 + 1.
match1(Wins, [X|Nums], N) :- \+ member(X, Wins), match1(Wins, Nums, N).
match(Input, Nth, NMatches) :-
nth1(Nth, Input, [Wins|CardNums]),
match1(Wins, CardNums, NMatches).
% sum(Cards, X, StuffToSum, Indices, Sum).
sum(_, _, [], [0], 0).
sum(Cards, X, [Element|Rest], [I,INext|IRest], Sum) :-
sum(Cards, X, Rest, [INext|IRest], SumOfRest),
Sum is Element + SumOfRest,
I is INext + 1,
match(Cards, I, NMatches_i), NMatches_i >= X - I.
sum(Cards, X, [_|Rest], [I,INext|IRest], SumOfRest) :-
sum(Cards, X, Rest, [INext|IRest], SumOfRest),
I is INext + 1,
match(Cards, I, NMatches_i), NMatches_i < X - I.
% Number of card X = Nx = 1 + sum(Ni*(matches(i) >= x-i), i=1->x-1)
ncards([], []).
ncards([_|RestOfCards], [Nx|NRest]) :-
@ -30,6 +9,25 @@ ncards([_|RestOfCards], [Nx|NRest]) :-
reverse(RestOfCards, ReversedRestOfCards),
sum(ReversedRestOfCards, X, NRest, _, Nx_minus_1), Nx is Nx_minus_1 + 1.
% sum(Cards, X, StuffToSum, Indices, Sum).
% This calculates the "sum(Ni*(matches(i) >= x-i), i=1->x-1)" part of Nx
sum(_, _, [], [0], 0).
sum(Cards, X, [Element|Rest], [I,INext|IRest], Sum) :-
sum(Cards, X, Rest, [INext|IRest], SumOfRest),
match(Cards, I, NMatches_i),
I is INext + 1,
(NMatches_i >= X - I -> Sum is Element + SumOfRest; Sum is SumOfRest).
% match binds the number of matches that card Nth in the list has
match(Cards, Nth, NMatches) :-
nth1(Nth, Cards, [Wins|CardNums]),
match1(Wins, CardNums, NMatches).
% match1(WinningNums, CardNums, NMatches) binds number of matches for a card.
match1(_, [], 0).
match1(Wins, [X|Nums], M) :- member(X, Wins), match1(Wins, Nums, M1), M is M1 + 1.
match1(Wins, [X|Nums], M) :- \+ member(X, Wins), match1(Wins, Nums, M).
% this is a more normal sum of a list
sum([], 0).
sum([Element|Rest], Sum) :- sum(Rest, RestOfSum), Sum is Element + RestOfSum.