| 1 | /* |
| 2 | * Copyright (c) 2005 The PseudoQ Project. |
| 3 | * |
| 4 | * This file is part of PseudoQ. |
| 5 | * |
| 6 | * PseudoQ is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU Lesser General Public License as published by |
| 8 | * the Free Software Foundation; either version 2.1 of the License, or |
| 9 | * (at your option) any later version. |
| 10 | * |
| 11 | * PseudoQ is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | * GNU Lesser General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU Lesser General Public License |
| 17 | * along with PseudoQ; if not, write to the Free Software |
| 18 | * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| 19 | */ |
| 20 | |
| 21 | package net.sourceforge.pseudoq.solver; |
| 22 | |
| 23 | import net.sourceforge.pseudoq.model.Coordinate; |
| 24 | import net.sourceforge.pseudoq.model.Grid; |
| 25 | |
| 26 | /** |
| 27 | * Puzzle-solving strategy that checks a single cell to see if there is only one |
| 28 | * possible value that can go there. |
| 29 | * @author <a href="http://sourceforge.net/users/stevensa">Andrew Stevens</a> |
| 30 | */ |
| 31 | public class SingleCellStrategy implements Strategy { |
| 32 | /** Log4J logger */ |
| 33 | private static final org.apache.log4j.Logger log = |
| 34 | org.apache.log4j.LogManager.getLogger(SingleCellStrategy.class); |
| 35 | |
| 36 | private Grid grid; |
| 37 | private Coordinate coord; |
| 38 | private CellPossibilitiesCounter counter; |
| 39 | |
| 40 | /** Creates a new instance of SingleCellStrategy */ |
| 41 | public SingleCellStrategy(Coordinate coord, Grid grid, Counter counter) { |
| 42 | if (coord == null) { |
| 43 | throw new IllegalArgumentException("Can't create strategy for null coord"); |
| 44 | } |
| 45 | if (grid == null) { |
| 46 | throw new IllegalArgumentException("Can't create strategy for null grid"); |
| 47 | } |
| 48 | if (counter == null) { |
| 49 | throw new IllegalArgumentException("Can't create strategy for null counter"); |
| 50 | } |
| 51 | if (!(counter instanceof CellPossibilitiesCounter)) { |
| 52 | throw new IllegalArgumentException("SingleCellStrategy needs a CellPossibilitiesCounter"); |
| 53 | } |
| 54 | |
| 55 | this.coord = coord; |
| 56 | this.grid = grid; |
| 57 | this.counter = (CellPossibilitiesCounter) counter; |
| 58 | } |
| 59 | |
| 60 | public SolutionStep evaluate() throws ObsoleteStrategyException, UnsolveablePuzzleException { |
| 61 | assert (coord != null); |
| 62 | assert (grid != null); |
| 63 | assert (counter != null); |
| 64 | |
| 65 | SolutionStep nextStep = null; |
| 66 | |
| 67 | if (!Integer.valueOf(0).equals(grid.get(coord))) { |
| 68 | throw new ObsoleteStrategyException(coord.toString() + " filled"); |
| 69 | } |
| 70 | if (counter.getCount() == 0) { |
| 71 | throw new UnsolveablePuzzleException(this.toString()); |
| 72 | } else if (counter.getCount() == 1) { |
| 73 | log.debug("Only one possibility left for " + coord.toString()); |
| 74 | int value = counter.getPossibilities().get(0).intValue(); |
| 75 | nextStep = new SolutionStep(coord, value, this.toString()); |
| 76 | } |
| 77 | |
| 78 | return nextStep; |
| 79 | } |
| 80 | |
| 81 | public String toString() { |
| 82 | return "SingleCell " + coord.toString(); |
| 83 | } |
| 84 | |
| 85 | } |