% Another minesweeper end game
% In the last few steps of a minesweeper game you have a single mine to flag
% There are 3 mines somewhere in the 6 squares in the bottom right hand corner of the board
% The corner looks like this ( f is a flag, U,V,W, X, Y, Z are unknown squares)
%   2 f 2 0
% 1 2 f 3 1
% 1 2 3 U V
% 1 1 f W X
%   1 2 Y Z
% Where is the best place to play to avoid hiting a mine and what are the odds?

% Encode U, ..., Z as 1 for a mine and 0 for no mine on that square
% b(X) -- bit X, X is either 0 or 1.
b(1). b(0).

:-dynamic(counters/6).
counters(0,0,0,0,0,0).

:-dynamic(total/1).
total(0).


% orginal problem
where(Field):-Field=[U,V,W, X, Y, Z], 
     b(U), b(V), b(W), b(X), b(Y),
     Z is 3-Y-X-W-V-U, b(Z),
     1 is U+V,
     3 is 2+U+V,
     3 is 2+U+W,
     2 is 1+Y+Z.
% Optimized
where2(Field):-Field=[U,V,W, X, Y, Z], 
     b(U), V is 1-U, W is 1-U,
     b(W), b(X), b(Y),
     Z is 3-Y-X-W-V-U, b(Z),
     1 is Y+Z.

field(F):-F=[U1,V1,W1,X1,Y1,Z1],
	write(U1), write('\t'), write(V1), nl,
	write(W1), write('\t'), write(X1), nl,
	write(Y1), write('\t'), write(Z1), nl.

go:-where(Field), count(Field), fail.
results:-counters(U,V, W,X,Y,Z), total(T),
	U1 is 100.0*U/T, write(U1), write('\t'),
	V1 is 100.0*V/T, write(V1), nl,
	W1 is 100.0*W/T, write(W1), write('\t'),
	X1 is 100.0*X/T, write(X1), nl,
	Y1 is 100.0*Y/T, write(Y1), write('\t'),
	Z1 is 100.0*Z/T, write(Z1), nl.
reset:-retract(counters(_,_,_,_,_,_)), assert(counters(0,0,0,0,0,0)), retract(total(_)), assert(total(0)).


count(Field):-retract(total(T0)), T1 is T0+1, assert(total(T1)),
	retract(counters(U0,V0,W0, X0, Y0, Z0)), Field=[U,V,W,X,Y,Z],
	U1 is U0+U, V1 is V0+V, W1 is W0+W, X1 is X0+X, Y1 is Y0+Y, Z1 is Z0+Z,
	assert(counters(U1,V1,W1,X1,Y1,Z1)).