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tdegames/kreversi/Position.cpp

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/* Yo Emacs, this -*- C++ -*-
*******************************************************************
*******************************************************************
*
*
* KREVERSI
*
*
*******************************************************************
*
* A Reversi (or sometimes called Othello) game
*
*******************************************************************
*
* Created 1997 by Mario Weilguni <mweilguni@sime.com>. This file
* is ported from Mats Luthman's <Mats.Luthman@sylog.se> JAVA applet.
* Many thanks to Mr. Luthman who has allowed me to put this port
* under the GNU GPL. Without his wonderful game engine kreversi
* would be just another of those Reversi programs a five year old
* child could beat easily. But with it it's a worthy opponent!
*
* If you are interested on the JAVA applet of Mr. Luthman take a
* look at http://www.sylog.se/~mats/
*
*******************************************************************
*
* This file is part of the KDE project "KREVERSI"
*
* KREVERSI is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* KREVERSI is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with KREVERSI; see the file COPYING. If not, write to
* the Free Software Foundation, 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
*******************************************************************
*/
// The class Position is used to represent an Othello position as white and
// black pieces and empty squares (see class Score) on an 8x8 Othello board.
#include "kdebug.h"
#include "Position.h"
#include <stdlib.h>
Position::Position()
{
setupStartPosition();
}
Position::Position(Position &pos, SimpleMove &move)
{
constrCopy(pos, move);
}
Position &Position::operator=(Position &pos)
{
// Copy the position itself.
for (uint row = 0; row < 10; row++)
for (uint col = 0; col < 10; col++)
m_board[row][col] = pos.m_board[row][col];
m_toMove = pos.m_toMove;
m_score = pos.m_score;
return *this;
}
// ----------------------------------------------------------------
// Helpers to the constructors
// Construct a Position by copying another one and then make a move.
//
void Position::constrCopy(Position &pos, SimpleMove &move)
{
*this = pos;
doMove(move);
}
// Setup the Position by setting it to the initial Reversi position.
void Position::setupStartPosition()
{
// Initialize the real board
for (uint i = 0; i < 10; i++)
for (uint j = 0; j < 10; j++)
m_board[i][j] = Nobody;
// The initial position
m_board[4][4] = White;
m_board[5][5] = White;
m_board[5][4] = Black;
m_board[4][5] = Black;
// Black always starts the game in Reversi.
m_toMove = Black;
// Each side starts out with two pieces.
m_score.set(White, 2);
m_score.set(Black, 2);
}
// ----------------------------------------------------------------
// Access methods
Color Position::color(uint x, uint y) const
{
if (x < 1 || x > 8 || y < 1 || y > 8)
return Nobody;
return m_board[x][y];
}
// ----------------------------------------------------------------
// Moves in the position
// Return true if the move is legal.
//
// NOTE: This function does *NOT* test wether the move is done
// by the color to move. That must be checked separately.
//
bool Position::moveIsLegal(SimpleMove &move) const
{
if (m_board[move.x()][move.y()] != Nobody)
return false;
Color color = move.color();
Color opponent = ::opponent(color);
// Check in all directions and see if there is a turnable row of
// opponent pieces. If there is at least one such row, then the
// move is legal.
for (int xinc = -1; xinc <= 1; xinc++) {
for (int yinc = -1; yinc <= 1; yinc++) {
int x, y;
if (xinc == 0 && yinc == 0)
continue;
// Find the end of such a row of pieces.
for (x = move.x()+xinc, y = move.y()+yinc; m_board[x][y] == opponent;
x += xinc, y += yinc)
;
// If the row ends with a piece of our own and there was at
// least one opponent piece between it and the move point, then
// we have found a turnable row.
if (m_board[x][y] == color
&& (x - xinc != move.x() || y - yinc != move.y()))
return true;
}
}
return false;
}
// See if 'color' can make a move in the current position. This is
// independent of wether it is 'color's turn to move or not.
bool Position::moveIsPossible(Color color) const
{
// Make it simple: Step through all squares and see if it is a legal move.
for (uint i = 1; i < 9; i++)
for (uint j = 1; j < 9; j++) {
SimpleMove move(color, i, j);
if (moveIsLegal(move))
return true;
}
return false;
}
// Return true if any side can move. (If not, the game is over.)
bool Position::moveIsAtAllPossible() const
{
return (moveIsPossible(White) || moveIsPossible(Black));
}
// Make a move in the position.
//
// Return true if the move was legal, otherwise return false.
//
bool Position::doMove(SimpleMove &move, QValueList<char> *turned)
{
if (move.color() == Nobody)
return false;
Color color = move.color();
Color opponent = ::opponent(color);
// Put the piece on the board
m_board[move.x()][move.y()] = color;
m_score.inc(color);
// Turn pieces.
uint scoreBefore = m_score.score(color);
for (int xinc = -1; xinc <= 1; xinc++) {
for (int yinc = -1; yinc <= 1; yinc++) {
int x, y;
// Skip the case where both xinc and yinc == 0, since then we
// won't move in any direction at all.
if (xinc == 0 && yinc == 0)
continue;
// Find the end point (x, y) of a possible row of turnable pieces.
for (x = move.x()+xinc, y = move.y()+yinc; m_board[x][y] == opponent;
x += xinc, y += yinc)
;
// If the row was indeed turnable, then do it.
if (m_board[x][y] == color) {
for (x -= xinc, y -= yinc; x != move.x() || y != move.y();
x -= xinc, y -= yinc) {
// Turn the piece.
m_board[x][y] = color;
if (turned)
turned->append(10 * x + y);
// Make the piece count correct again.
m_score.inc(color);
m_score.dec(opponent);
}
}
}
}
// If nothing was turned, the move wasn't legal.
if (m_score.score(color) == scoreBefore) {
m_board[move.x()][move.y()] = Nobody;
m_score.dec(color);
return false;
}
// Set the next color to move.
if (moveIsPossible(opponent))
m_toMove = opponent;
else if (moveIsPossible(color))
m_toMove = color;
else
m_toMove = Nobody;
return true;
}
bool Position::doMove(Move &move)
{
move.m_turnedPieces.clear();
return doMove((SimpleMove &) move, &move.m_turnedPieces);
}
bool Position::undoMove(Move &move)
{
Color color = move.color();
Color other = opponent(color);
// Sanity checks
// 1. The move must be on the board and be of the right color.
if (color != m_board[move.x()][move.y()]) {
//kdDebug() << "move on the board is wrong color: " << (int) color << "["
// << move.x() << "," << move.y() << "]" << endl;
return false;
}
// 2. All turned pieces must be on the board anb be of the right color.
QValueList<char>::iterator it;
for (it = move.m_turnedPieces.begin();
it != move.m_turnedPieces.end();
++it) {
int sq = *it;
if (m_board[sq / 10][sq % 10] != color) {
//kdDebug() << "turned piece the board is wrong color: ["
// << sq / 10 << "," << sq % 10 << "]" << endl;
return false;
}
}
// Ok, everything seems allright. Let's do it!
// 1. Unturn all the turned pieces.
for (it = move.m_turnedPieces.begin();
it != move.m_turnedPieces.end();
++it) {
int sq = *it;
m_board[sq / 10][sq % 10] = other;
m_score.dec(color);
m_score.inc(other);
}
// 2. Remove the move itself.
m_score.dec(color);
m_board[move.x()][move.y()] = Nobody;
return true;
}
MoveList Position::generateMoves(Color color) const
{
MoveList moves;
// Make it simple: Step through all squares and see if it is a legal move.
for (uint i = 1; i < 9; i++) {
for (uint j = 1; j < 9; j++) {
Move move(color, i, j);
if (moveIsLegal(move))
moves.append(move);
}
}
return moves;
}
QString Position::asString() const
{
QString result;
for (uint y = 1; y < 9; ++y) {
for (uint x = 1; x < 9; ++x) {
switch (m_board[x][y]) {
case Nobody: result.append(' '); break;
case Black: result.append('*'); break;
case White: result.append('o'); break;
default: result.append('?'); break;
}
}
result.append('\n');
}
return result;
}