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/* $NetBSD: algor.cc,v 1.5 2012/02/29 23:39:53 joerg Exp $ */
/*-
* Copyright (c) 2003 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Christos Zoulas.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* algor.C: Computer algorithm
*/
#include "defs.h"
RCSID("$NetBSD: algor.cc,v 1.5 2012/02/29 23:39:53 joerg Exp $")
#include "algor.h"
#include "board.h"
#include "box.h"
#include "random.h"
ALGOR::ALGOR(const char c) : PLAYER(c)
{
#ifdef notyet
// Single Edges = (x + y) * 2
_edge1 = (_b.nx() * _b.ny()) * 2;
// Shared Edges = (x * (y - 1)) + ((x - 1) * y)
_edge2 = (_b.nx() * (_b.ny() - 1)) + ((_b.nx() - 1) * _b.ny());
// Maximum Edges filled before closure = x * y * 2
_maxedge = _b.nx() * _b.ny() * 2;
#endif
}
// Find the first closure, i.e. a box that has 3 edges
int ALGOR::find_closure(size_t& y, size_t& x, int& dir, BOARD& b)
{
RANDOM rdy(b.ny()), rdx(b.nx());
for (y = rdy(); y < b.ny(); y = rdy()) {
rdx.clear();
for (x = rdx(); x < b.nx(); x = rdx()) {
BOX box(y, x, b);
if (box.count() == 3) {
for (dir = BOX::first; dir < BOX::last; dir++)
if (!box.isset(dir))
return 1;
b.abort("find_closure: 3 sided box[%zu,%zu] has no free sides",
y, x);
}
}
}
return 0;
}
#if 0
size_t ALGOR::find_single()
{
size_t ne;
// Find the number of single edges in use
for (size_t x = 0; x < b.nx(); x++) {
BOX tbox(0, x, b);
ne += tbox.isset(BOX::top);
BOX bbox(b.ny() - 1, x, b);
ne += bbox.isset(BOX::bottom);
}
for (size_t y = 0; y < _b.ny(); y++) {
BOX lbox(y, 0, b);
ne += lbox.isset(BOX::left);
BOX rbox(y,_b.nx() - 1, b);
ne += rbox.isset(BOX::right);
}
return ne;
}
#endif
// Count a closure, by counting all boxes that we can close in the current
// move
size_t ALGOR::count_closure(size_t& y, size_t& x, int& dir, BOARD& b)
{
size_t i = 0;
size_t tx, ty;
int tdir, mv;
while (find_closure(ty, tx, tdir, b)) {
if (i == 0) {
// Mark the beginning of the closure
x = tx;
y = ty;
dir = tdir;
}
if ((mv = b.domove(ty, tx, tdir, getWho())) == -1)
b.abort("count_closure: Invalid move (%zu, %zu, %d)", y, x, dir);
else
i += mv;
}
return i;
}
/*
* Find the largest closure, by closing all possible closures.
* return the number of boxes closed in the maximum closure,
* and the first box of the maximum closure in (x, y, dir)
*/
size_t ALGOR::find_max_closure(size_t& y, size_t& x, int& dir, const BOARD& b)
{
BOARD nb(b);
int maxdir = -1;
size_t nbox, maxbox = 0;
size_t maxx = ~0, maxy = ~0;
size_t tx = 0, ty = 0; /* XXX: GCC */
int tdir = 0; /* XXX: GCC */
while ((nbox = count_closure(ty, tx, tdir, nb)) != 0)
if (nbox > maxbox) {
// This closure is better, update max
maxbox = nbox;
maxx = tx;
maxy = ty;
maxdir = tdir;
}
// Return the max found
y = maxy;
x = maxx;
dir = maxdir;
return maxbox;
}
// Find if a turn does not result in a capture on the given box
// and return the direction if found.
int ALGOR::try_good_turn(BOX& box, size_t y, size_t x, int& dir, BOARD& b)
{
// Sanity check; we must have a good box
if (box.count() >= 2)
b.abort("try_good_turn: box[%zu,%zu] has more than 2 sides occupied",
y, x);
// Make sure we don't make a closure in an adjacent box.
// We use a random direction to randomize the game
RANDOM rd(BOX::last);
for (dir = rd(); dir < BOX::last; dir = rd())
if (!box.isset(dir)) {
size_t by = y + BOX::edges[dir].y;
size_t bx = x + BOX::edges[dir].x;
if (!b.bounds(by, bx))
return 1;
BOX nbox(by, bx, b);
if (nbox.count() < 2)
return 1;
}
return 0;
}
// Try to find a turn that does not result in an opponent closure, and
// return it in (x, y, dir); if not found return 0.
int ALGOR::find_good_turn(size_t& y, size_t& x, int& dir, const BOARD& b)
{
BOARD nb(b);
RANDOM rdy(b.ny()), rdx(b.nx());
for (y = rdy(); y < b.ny(); y = rdy()) {
rdx.clear();
for (x = rdx(); x < b.nx(); x = rdx()) {
BOX box(y, x, nb);
if (box.count() < 2 && try_good_turn(box, y, x, dir, nb))
return 1;
}
}
return 0;
}
// On a box with 2 edges, return the first or the last free edge, depending
// on the order specified
int ALGOR::try_bad_turn(BOX& box, size_t& y, size_t& x, int& dir, BOARD& b,
int last)
{
if (4 - box.count() <= last)
b.abort("try_bad_turn: Called at [%zu,%zu] for %d with %d",
y, x, last, box.count());
for (dir = BOX::first; dir < BOX::last; dir++)
if (!box.isset(dir)) {
if (!last)
return 1;
else
last--;
}
return 0;
}
// Find a box that has 2 edges and return the first free edge of that
// box or the last free edge of that box
int ALGOR::find_bad_turn(size_t& y, size_t& x, int& dir, BOARD& b, int last)
{
RANDOM rdy(b.ny()), rdx(b.nx());
for (y = rdy(); y < b.ny(); y = rdy()) {
rdx.clear();
for (x = rdx(); x < b.nx(); x = rdx()) {
BOX box(y, x, b);
if ((4 - box.count()) > last &&
try_bad_turn(box, y, x, dir, b, last))
return 1;
}
}
return 0;
}
size_t ALGOR::find_min_closure1(size_t& y, size_t& x, int& dir, const BOARD& b,
int last)
{
BOARD nb(b);
int tdir, mindir = -1, mv;
// number of boxes per closure
size_t nbox, minbox = nb.nx() * nb.ny() + 1;
size_t tx, ty, minx = ~0, miny = ~0;
int xdir = 0; /* XXX: GCC */
while (find_bad_turn(ty, tx, tdir, nb, last)) {
// Play a bad move that would cause the opponent's closure
if ((mv = nb.domove(ty, tx, tdir, getWho())) != 0)
b.abort("find_min_closure1: Invalid move %d (%zu, %zu, %d)", mv,
ty, tx, tdir);
// Count the opponent's closure
if ((nbox = count_closure(y, x, xdir, nb)) == 0)
b.abort("find_min_closure1: no closure found");
if (nbox <= minbox) {
// This closure has fewer boxes
minbox = nbox;
minx = tx;
miny = ty;
mindir = tdir;
}
}
y = miny;
x = minx;
dir = mindir;
return minbox;
}
// Search for the move that makes the opponent close the least number of
// boxes; returns 1 if a move found, 0 otherwise
size_t ALGOR::find_min_closure(size_t& y, size_t& x, int& dir, const BOARD& b)
{
size_t x1, y1;
int dir1;
size_t count = b.ny() * b.nx() + 1, count1;
for (size_t i = 0; i < 3; i++)
if (count > (count1 = find_min_closure1(y1, x1, dir1, b, i))) {
count = count1;
y = y1;
x = x1;
dir = dir1;
}
return count != b.ny() * b.nx() + 1;
}
// Return a move in (y, x, dir)
void ALGOR::play(const BOARD& b, size_t& y, size_t& x, int& dir)
{
// See if we can close the largest closure available
if (find_max_closure(y, x, dir, b))
return;
#ifdef notyet
size_t sgl = find_single();
size_t dbl = find_double();
#endif
// See if we can play an edge without giving the opponent a box
if (find_good_turn(y, x, dir, b))
return;
// Too bad, find the move that gives the opponent the fewer boxes
if (find_min_closure(y, x, dir, b))
return;
}
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