001package ball.game.sudoku; 002/*- 003 * ########################################################################## 004 * Game Applications and Utilities 005 * $Id: RuleOfElimination.java 5285 2020-02-05 04:23:21Z ball $ 006 * $HeadURL: svn+ssh://svn.hcf.dev/var/spool/scm/repository.svn/ball-game/trunk/src/main/java/ball/game/sudoku/RuleOfElimination.java $ 007 * %% 008 * Copyright (C) 2010 - 2020 Allen D. Ball 009 * %% 010 * Licensed under the Apache License, Version 2.0 (the "License"); 011 * you may not use this file except in compliance with the License. 012 * You may obtain a copy of the License at 013 * 014 * http://www.apache.org/licenses/LICENSE-2.0 015 * 016 * Unless required by applicable law or agreed to in writing, software 017 * distributed under the License is distributed on an "AS IS" BASIS, 018 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 019 * See the License for the specific language governing permissions and 020 * limitations under the License. 021 * ########################################################################## 022 */ 023import lombok.NoArgsConstructor; 024import lombok.ToString; 025import ball.annotation.ServiceProviderFor; 026import ball.util.CoordinateMap; 027 028/** 029 * Sudoku "rule-of-elimination" {@link Rule} implementation. If a digit is 030 * the solution to a {@link Cell} then it cannot be the solution to any 031 * other {@link Cell} in the row, column, or 3x3 nonet. 032 * 033 * @author {@link.uri mailto:ball@hcf.dev Allen D. Ball} 034 * @version $Revision: 5285 $ 035 */ 036@ServiceProviderFor({ Rule.class }) 037@NoArgsConstructor @ToString 038public class RuleOfElimination extends Rule { 039 @Override 040 public boolean applyTo(Puzzle puzzle) { 041 boolean modified = false; 042 043 for (;;) { 044 if (iterate(puzzle)) { 045 modified |= true; 046 } else { 047 break; 048 } 049 } 050 051 return modified; 052 } 053 054 private boolean iterate(Puzzle puzzle) { 055 boolean modified = false; 056 057 for (Cell cell : puzzle.values()) { 058 if (cell.isSolved()) { 059 for (CoordinateMap<Cell> map : puzzle.subMapsOf(cell)) { 060 for (Cell other : map.values()) { 061 if (other != cell) { 062 modified |= other.removeAll(cell); 063 } 064 } 065 } 066 } 067 } 068 069 return modified; 070 } 071}