Sudoku: src/main/java/de/uapcore/sudoku/Solver.java@569220009c54 (annotated)

src/main/java/de/uapcore/sudoku/Solver.java@569220009c54 (annotated)

src/main/java/de/uapcore/sudoku/Solver.java

Wed, 26 Aug 2020 19:09:07 +0200

author: Mike Becker <universe@uap-core.de>
date: Wed, 26 Aug 2020 19:09:07 +0200
changeset 25: 569220009c54
parent 12: 1c62c6009161
permissions: -rw-r--r--

fixes wrong call of assertEquals()

 /*
  * Copyright 2013 Mike Becker. All rights reserved.
  *
  * 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 COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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.
  */
 package de.uapcore.sudoku;
 import java.util.ArrayList;
 import java.util.List;
 /**
  * Implements the backtracking algorithm for solving the Sudoku.
  */
 public final class Solver {
     private Integer fillInCandidate(Field f, List<Integer>[][] candidates, int x, int y) {
         Integer c = candidates[x][y].remove(0);
         f.setCellValue(x, y, c);
         f.setCellModified(x, y, true);
         for (int i = 0 ; i < 9 ; i++) {
             candidates[x][i].remove(c);
             candidates[i][y].remove(c);
         }
         for (int i = 0 ; i < 3 ; i++) {
             for (int j = 0 ; j < 3 ; j++) {
                 candidates[x-x%3+i][y-y%3+j].remove(c);
             }
         }
         return c;
     }
     private void makeBackup(List<Integer>[][] candidates, List<Integer>[][] candidatesBackup) {
         for (int x = 0 ; x < 9 ; x++) {
             for (int y = 0 ; y < 9 ; y++) {
                 candidatesBackup[x][y] = new ArrayList<>(9);
                 candidatesBackup[x][y].addAll(candidates[x][y]);
             }
         }
     }
     private void makeBackup(Field f, int[][] fieldBackup) {
         for (int x = 0 ; x < 9 ; x++) {
             for (int y = 0 ; y < 9 ; y++) {
                 fieldBackup[x][y] = f.getCellValue(x, y);
             }
         }
     }
     private void restoreBackup(Field f, int[][] fieldBackup) {
         for (int x = 0 ; x < 9 ; x++) {
             for (int y = 0 ; y < 9 ; y++) {
                 f.setCellValue(x, y, fieldBackup[x][y]);
             }
         }
     }
     private void restoreBackup(List<Integer>[][] candidates, List<Integer>[][] candidatesBackup) {
         for (int x = 0 ; x < 9 ; x++) {
             for (int y = 0 ; y < 9 ; y++) {
                 candidates[x][y].clear();
                 candidates[x][y].addAll(candidatesBackup[x][y]);
             }
         }
     }
     private boolean solve(Field f, List<Integer>[][] candidates) {
         // Make backup
         List<Integer>[][] candidatesBackup = new List[9][9];
         int[][] fieldBackup = new int[9][9];
         makeBackup(candidates, candidatesBackup);
         makeBackup(f, fieldBackup);
         // Fill in distinct solutions
         boolean fillDistinct;
         do {
             fillDistinct = false;
             for (int x = 0 ; x < 9 ; x++) {
                 for (int y = 0 ; y < 9 ; y++) {
                     if (f.isCellEmpty(x, y) && candidates[x][y].size() == 1) {
                         fillInCandidate(f, candidates, x, y);
                         fillDistinct = true;
                     }
                 }
             }
         } while (fillDistinct);
         // Try out remaining candidates
         for (int x = 0 ; x < 9 ; x++) {
             for (int y = 0 ; y < 9 ; y++) {
                 if (f.isCellEmpty(x, y)) {
                     while (candidates[x][y].size() > 0) {
                         List<Integer>[][] cb = new List[9][9];
                         makeBackup(candidates, cb);
                         Integer c = fillInCandidate(f, candidates, x, y);
                         if (solve(f, candidates)) {
                             break;
                         } else {
                             f.clearCellValue(x, y);
                             restoreBackup(candidates, cb);
                             // Remove current candidate anyway
                             candidates[x][y].remove(c);
                         }
                     }
                 }
                 if (f.isCellEmpty(x, y)) {
                     restoreBackup(f, fieldBackup);
                     restoreBackup(candidates, candidatesBackup);
                     return false;
                 }
             }
         }
         return true;
     }
     /**
      * Attempts to solve the given Sudoku field.
      *
      * The solution, if any, is directly entered into the field.
      * All solved fields will be in modified state.
      * The already given fields are left untouched.
      *
      * @param f the field to solve
      * @return true if a solution could be found, false if the field is unsolvable
      */
     public boolean solve(Field f) {
         // Calculate initial candidates
         List<Integer>[][] candidates = new List[9][9];
         for (int x = 0 ; x < 9 ; x++) {
             for (int y = 0 ; y < 9 ; y++) {
                 candidates[x][y] = new ArrayList<>(9);
                 if (f.getCellValue(x, y) == 0) {
                     // All numbers are candidates
                     for (int c = 1 ; c <= 9 ; c++) {
                         candidates[x][y].add(c);
                     }
                     // Remove row duplicates
                     int[] line = f.getRow(y);
                     for (Integer c : line) {
                         candidates[x][y].remove(c);
                     }
                     // Remove column duplicates
                     line = f.getColumn(x);
                     for (Integer c : line) {
                         candidates[x][y].remove(c);
                     }
                     // Remove square duplicates
                     int[][] square = f.getSquare(x/3, y/3);
                     for (int[] sq : square) {
                         for (Integer c : sq) {
                             candidates[x][y].remove(c);
                         }
                     }
                 }
             }
         }
         // Backtrack
         return solve(f, candidates);
     }
     /**
      * Performs a fast check whether any field violates the Sudoku rules.
      *
      * @param f the field to check
      * @return true, if the check succeeds, false otherwise
      */
     public boolean check(Field f) {
         int[] line;
         for (int i = 0 ; i < 9 ; i++) {
             line = f.getRow(i);
             if (!valid(line)) {
                 return false;
             }
             line = f.getColumn(i);
             if (!valid(line)) {
                 return false;
             }
         }
         int[][] square;
         for (int x = 0 ; x < 3 ; x++) {
             for (int y = 0 ; y < 3 ; y++) {
                 square = f.getSquare(x, y);
                 if (!valid(square)) {
                     return false;
                 }
             }
         }
         return true;
     }
     private boolean valid(int[] line) {
         int[] numbers;
         numbers = new int[9];
         for (int i = 0 ; i < 9 ; i++) {
             int l = line[i]-1;
             if (l >= 0) {
                 if ((++numbers[l]) > 1) {
                     return false;
                 }
             }
         }
         return true;
     }
     private boolean valid(int[][] square) {
         int[] line = new int[9];
         for (int x = 0 ; x < 3 ; x++) {
             System.arraycopy(square[x], 0, line, 3*x, 3);
         }
         return valid(line);
     }
 }

Mercurial > hg > Sudoku / annotate

src/main/java/de/uapcore/sudoku/Solver.java@569220009c54 (annotated)

src/main/java/de/uapcore/sudoku/Solver.java