1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/main/java/de/uapcore/sudoku/Solver.java Sat Jul 25 14:01:28 2020 +0200
1.3 @@ -0,0 +1,227 @@
1.4 +/*
1.5 + * Copyright 2013 Mike Becker. All rights reserved.
1.6 + *
1.7 + * Redistribution and use in source and binary forms, with or without
1.8 + * modification, are permitted provided that the following conditions are met:
1.9 + *
1.10 + * 1. Redistributions of source code must retain the above copyright
1.11 + * notice, this list of conditions and the following disclaimer.
1.12 + *
1.13 + * 2. Redistributions in binary form must reproduce the above copyright
1.14 + * notice, this list of conditions and the following disclaimer in the
1.15 + * documentation and/or other materials provided with the distribution.
1.16 + *
1.17 + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
1.18 + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
1.19 + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
1.20 + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
1.21 + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
1.22 + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
1.23 + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
1.24 + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
1.25 + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
1.26 + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
1.27 + * POSSIBILITY OF SUCH DAMAGE.
1.28 + */
1.29 +
1.30 +package de.uapcore.sudoku;
1.31 +
1.32 +import java.util.ArrayList;
1.33 +import java.util.List;
1.34 +
1.35 +/**
1.36 + *
1.37 + * @author mike
1.38 + */
1.39 +public final class Solver {
1.40 +
1.41 + public Solver() {
1.42 + }
1.43 +
1.44 + private Integer fillInCandidate(Field f, List<Integer>[][] candidates, int x, int y) {
1.45 + Integer c = candidates[x][y].remove(0);
1.46 + f.setCellValue(x, y, c);
1.47 + f.setCellModified(x, y, true);
1.48 + for (int i = 0 ; i < 9 ; i++) {
1.49 + candidates[x][i].remove(c);
1.50 + candidates[i][y].remove(c);
1.51 + }
1.52 + for (int i = 0 ; i < 3 ; i++) {
1.53 + for (int j = 0 ; j < 3 ; j++) {
1.54 + candidates[x-x%3+i][y-y%3+j].remove(c);
1.55 + }
1.56 + }
1.57 + return c;
1.58 + }
1.59 +
1.60 + private void makeBackup(List<Integer>[][] candidates, List<Integer>[][] candidatesBackup) {
1.61 + for (int x = 0 ; x < 9 ; x++) {
1.62 + for (int y = 0 ; y < 9 ; y++) {
1.63 + candidatesBackup[x][y] = new ArrayList<>(9);
1.64 + candidatesBackup[x][y].addAll(candidates[x][y]);
1.65 + }
1.66 + }
1.67 + }
1.68 +
1.69 + private void makeBackup(Field f, int[][] fieldBackup) {
1.70 + for (int x = 0 ; x < 9 ; x++) {
1.71 + for (int y = 0 ; y < 9 ; y++) {
1.72 + fieldBackup[x][y] = f.getCellValue(x, y);
1.73 + }
1.74 + }
1.75 + }
1.76 +
1.77 + private void restoreBackup(Field f, int[][] fieldBackup) {
1.78 + for (int x = 0 ; x < 9 ; x++) {
1.79 + for (int y = 0 ; y < 9 ; y++) {
1.80 + f.setCellValue(x, y, fieldBackup[x][y]);
1.81 + }
1.82 + }
1.83 + }
1.84 +
1.85 + private void restoreBackup(List<Integer>[][] candidates, List<Integer>[][] candidatesBackup) {
1.86 + for (int x = 0 ; x < 9 ; x++) {
1.87 + for (int y = 0 ; y < 9 ; y++) {
1.88 + candidates[x][y].clear();
1.89 + candidates[x][y].addAll(candidatesBackup[x][y]);
1.90 + }
1.91 + }
1.92 + }
1.93 +
1.94 + private boolean solve(Field f, List<Integer>[][] candidates) {
1.95 +
1.96 + // Make backup
1.97 + List<Integer>[][] candidatesBackup = new List[9][9];
1.98 + int[][] fieldBackup = new int[9][9];
1.99 + makeBackup(candidates, candidatesBackup);
1.100 + makeBackup(f, fieldBackup);
1.101 +
1.102 + // Fill in distinct solutions
1.103 + boolean fillDistinct;
1.104 + do {
1.105 + fillDistinct = false;
1.106 + for (int x = 0 ; x < 9 ; x++) {
1.107 + for (int y = 0 ; y < 9 ; y++) {
1.108 + if (f.isCellEmpty(x, y) && candidates[x][y].size() == 1) {
1.109 + fillInCandidate(f, candidates, x, y);
1.110 + fillDistinct = true;
1.111 + }
1.112 + }
1.113 + }
1.114 + } while (fillDistinct);
1.115 +
1.116 + // Try out remaining candidates
1.117 + for (int x = 0 ; x < 9 ; x++) {
1.118 + for (int y = 0 ; y < 9 ; y++) {
1.119 + if (f.isCellEmpty(x, y)) {
1.120 + while (candidates[x][y].size() > 0) {
1.121 + List<Integer>[][] cb = new List[9][9];
1.122 + makeBackup(candidates, cb);
1.123 + Integer c = fillInCandidate(f, candidates, x, y);
1.124 + if (solve(f, candidates)) {
1.125 + break;
1.126 + } else {
1.127 + f.clearCellValue(x, y);
1.128 + restoreBackup(candidates, cb);
1.129 + // Remove current candidate anyway
1.130 + candidates[x][y].remove(c);
1.131 + }
1.132 + }
1.133 + }
1.134 + if (f.isCellEmpty(x, y)) {
1.135 + restoreBackup(f, fieldBackup);
1.136 + restoreBackup(candidates, candidatesBackup);
1.137 + return false;
1.138 + }
1.139 + }
1.140 + }
1.141 +
1.142 + return true;
1.143 + }
1.144 +
1.145 + public boolean solve(Field f) {
1.146 +
1.147 + // Calculate initial candidates
1.148 + List<Integer> candidates[][] = new List[9][9];
1.149 + for (int x = 0 ; x < 9 ; x++) {
1.150 + for (int y = 0 ; y < 9 ; y++) {
1.151 + candidates[x][y] = new ArrayList<>(9);
1.152 + if (f.getCellValue(x, y) == 0) {
1.153 + // All numbers are candidates
1.154 + for (int c = 1 ; c <= 9 ; c++) {
1.155 + candidates[x][y].add(c);
1.156 + }
1.157 + // Remove row duplicates
1.158 + int[] line = f.getRow(y);
1.159 + for (Integer c : line) {
1.160 + candidates[x][y].remove(c);
1.161 + }
1.162 + // Remove column duplicates
1.163 + line = f.getColumn(x);
1.164 + for (Integer c : line) {
1.165 + candidates[x][y].remove(c);
1.166 + }
1.167 + // Remove square duplicates
1.168 + int[][] square = f.getSquare(x/3, y/3);
1.169 + for (int[] sq : square) {
1.170 + for (Integer c : sq) {
1.171 + candidates[x][y].remove(c);
1.172 + }
1.173 + }
1.174 + }
1.175 + }
1.176 + }
1.177 +
1.178 + // Backtrack
1.179 + return solve(f, candidates);
1.180 + }
1.181 +
1.182 + public boolean check(Field f) {
1.183 + int line[];
1.184 + for (int i = 0 ; i < 9 ; i++) {
1.185 + line = f.getRow(i);
1.186 + if (!valid(line)) {
1.187 + return false;
1.188 + }
1.189 + line = f.getColumn(i);
1.190 + if (!valid(line)) {
1.191 + return false;
1.192 + }
1.193 + }
1.194 +
1.195 + int square[][];
1.196 + for (int x = 0 ; x < 3 ; x++) {
1.197 + for (int y = 0 ; y < 3 ; y++) {
1.198 + square = f.getSquare(x, y);
1.199 + if (!valid(square)) {
1.200 + return false;
1.201 + }
1.202 + }
1.203 + }
1.204 +
1.205 + return true;
1.206 + }
1.207 +
1.208 + private boolean valid(int[] line) {
1.209 + int numbers[];
1.210 + numbers = new int[9];
1.211 + for (int i = 0 ; i < 9 ; i++) {
1.212 + int l = line[i]-1;
1.213 + if (l >= 0) {
1.214 + if ((++numbers[l]) > 1) {
1.215 + return false;
1.216 + }
1.217 + }
1.218 + }
1.219 +
1.220 + return true;
1.221 + }
1.222 +
1.223 + private boolean valid(int[][] square) {
1.224 + int[] line = new int[9];
1.225 + for (int x = 0 ; x < 3 ; x++) {
1.226 + System.arraycopy(square[x], 0, line, 3*x, 3);
1.227 + }
1.228 + return valid(line);
1.229 + }
1.230 +}
