Knight's tour: Difference between revisions
→{{header|ATS}}
Line 1,198:
in
array_set_at (!(chessboard.p_board), index, value)
end
extern fn {t : t@ype}
find_nth_position$equal (x : t,
y : t) :
bool
fn {t : t@ype}
find_nth_position
{n_ranks, n_files : pos}
(chessboard : !chessboard_vt (t, n_ranks, n_files),
n : t) :
[i, j : int]
move_t (i, j) =
let
val n_ranks = chessboard.n_ranks
val n_files = chessboard.n_files
fun
outer_loop {i : pos | i <= n_ranks + 1} .<n_ranks + 1 - i>.
(chessboard : !chessboard_vt (t, n_ranks, n_files),
i : int i) :
[i, j : int]
move_t (i, j) =
let
fun
inner_loop {j : pos | j <= n_files + 1} .<n_files + 1 - j>.
(chessboard : !chessboard_vt (t, n_ranks, n_files),
j : int j) :
[j : int]
int j =
if u2i n_files < j then
j
else
let
val v = chessboard_vt_get<t> (chessboard, i, j)
in
if find_nth_position$equal<t> (n, v) then
j
else
inner_loop (chessboard, succ j)
end
in
if u2i n_ranks < i then
nil_move
else
let
val j = inner_loop (chessboard, 1)
in
if j <= u2i n_files then
@(i, j)
else
outer_loop (chessboard, succ i)
end
end
in
outer_loop (chessboard, 1)
end
implement
find_nth_position$equal<int> (x, y) =
x = y
fn
knights_tour_is_closed
{n_ranks, n_files : pos}
(chessboard : !chessboard_vt (int, n_ranks, n_files)) :
bool =
let
val n_squares = chessboard.n_squares
val @(i1, j1) = find_nth_position<int> (chessboard, 1)
val @(i2, j2) = find_nth_position<int> (chessboard, u2i n_squares)
val i_diff = abs (i1 - i2)
val j_diff = abs (j1 - j2)
in
(i_diff = 1 && j_diff = 2) || (i_diff = 2 && j_diff = 1)
end
Line 1,335 ⟶ 1,411:
val _ = loop (positions, 0)
val _ = move_t_fprint (f, positions[pred n_squares])
val _ =
if knights_tour_is_closed (chessboard) then
fileref_puts (f, " -> cycle")
val _ = array_ptr_free (pf, pfgc | p_positions)
Line 1,715 ⟶ 1,794:
e3 -> g4 -> h6 -> g8 -> f6 -> h5 -> f4 -> d5 ->
e7 -> c8 -> a7 -> c6 -> e5 -> c4 -> b6 -> a8 ->
c7 -> e8 -> d6 -> b5 -> d4 -> f5 -> g7 -> e6 -> cycle
+----+----+----+----+----+----+----+----+
8 | 56 | 3 | 50 | 21 | 58 | 5 | 44 | 19 |
Line 1,743 ⟶ 1,822:
e3 -> g4 -> h6 -> g8 -> f6 -> h5 -> f4 -> d5 ->
e7 -> c8 -> a7 -> c6 -> e5 -> c4 -> b6 -> a8 ->
c7 -> b5 -> d6 -> e8 -> g7 -> f5 -> d4 -> e6 -> cycle
+----+----+----+----+----+----+----+----+
8 | 56 | 3 | 50 | 21 | 60 | 5 | 44 | 19 |
| |||