在 Prolog 中获取规则的最小值

Question

我正在尝试解决 Knight Tour 问题。我需要获得移动量最少的位置。我有计算某个位置移动次数的规则 (search_path)，但我需要获取该规则的最小值 (search_path_min)。

    moves(X, Y, Xi, Yi, Size) :-
    ( Xi is X - 1, Yi is Y - 2 
    ; Xi is X - 1, Yi is Y + 2 
    ; Xi is X + 1, Yi is Y - 2
    ; Xi is X + 1, Yi is Y + 2
    ; Xi is X - 2, Yi is Y - 1 
    ; Xi is X - 2, Yi is Y + 1 
    ; Xi is X + 2, Yi is Y - 1
    ; Xi is X + 2, Yi is Y + 1 ),
    Xi > 0,
    Yi > 0,
    Xi =< Size*Size,
    Yi =< Size*Size.

posibles_moves(Size, X, Y, Tour, Xi, Yi):-
    moves(X, Y, Xi, Yi, Size),
    \+ member((Xi,Yi),Tour).

posibles_moves_count(Size, X, Y, Tour, Count):-
    findall(_, posibles_moves(Size, X, Y, Tour, Xi, Yi), Moves),
    length(Moves, Count).

search_path(Size, X, Y, Tour, Xi, Yi, Count):-
    posibles_moves(Size, X, Y, Tour, Xi, Yi),
    posibles_moves_count(Size, Xi, Yi, [(Xi,Yi)|Tour],Count).

search_path_min(Size, X, Y, Tour, Xi, Yi):-
    search_path(Size, X, Y, Tour, Xi, Yi, Count),
    ?
    ?
    ?
    ?

knight_tour(Size, X, Y, Tour, Path) :-
    length(Tour, L),
    L =:= Size * Size - 1,
    _Tour = [(X, Y) | Tour],
    reverse(_Tour, Path).

knight_tour(Size, X, Y, Tour, Path) :-
    length(Visits, L),
    L < Size * Size - 1,
    search_path_min(Size, X, Y, Tour, Xi, Yi),
    _Tour = [(X, Y) | Tour],
    knight_tour(Size, Xi, Yi, _Tour, Path).

我的规则search_path 我需要获得具有 Count 变量最小值的结果。谢谢

Answer 1

我能解决

search_path_min(Size, X, Y, Tour, Minimum):-
    findall(min(Xi,Yi,Count),search_path(Size,X,Y,Tour,Xi,Yi,Count),[H|Rest]),
    search_path_min(H,Rest,Minimum).

search_path_min(Minimum, [], Minimum).

search_path_min(min(X,Y,C),[min(X2,Y2,C2)|Rest],Minimum):-
    C < C2 -> search_path_min(min(X,Y,C),Rest,Minimum);
              search_path_min(min(X2,Y2,C2),Rest,Minimum).

在 Prolog 中获取规则的最小值

Get min value of a rule in Prolog

prolog

knights-tour