sudoku

[hashimtk]

Hi,
i done a sudoku solving program ,and i got solution for easy sudoku, Can u explain any logic to find out medium and hard sudoku.

[r035198x]

Hi,
i done a sudoku solving program ,and i got solution for easy sudoku, Can u explain any logic to find out medium and hard sudoku.

I hope you went through this article.

[JosAH]

I wrote that article and solver and I'm curious how it behaves on 'difficult' problems.
Please let us know the results you find.

kind regards,

Jos

[hashimtk]

I wrote that article and solver and I'm curious how it behaves on 'difficult' problems.
Please let us know the results you find.

kind regards,

Jos

 package hitori;
 
public class Sudoku {
 
 
    public final static int puzzle[][] = {
        {2, 0, 0, 7, 4, 0, 8, 0, 1},      
        {8, 0, 0, 2, 9, 0, 5, 0, 6},
        {0, 7, 5, 0, 8, 0, 0, 0, 0},
        {0, 0, 0, 8, 2, 0, 6, 0, 0},
        {4, 0, 2, 0, 0, 0, 9, 0, 8},
        {0, 0, 3, 0, 6, 9, 0, 0, 0},
        {0, 0, 0, 0, 1, 0, 4, 6, 0},
        {3, 0, 1, 0, 7, 8, 0, 0, 9},
        {6, 0, 9, 0, 5, 4, 0, 0, 7}
    };
 
 
    static boolean possibilities[][][] = new boolean[9][9][9];
 
 
    public static void fillPossibilitiesMatrix() {
        for (int row =0; row <puzzle.length; row++) {
            for  (int column =0; column <puzzle.length; column++) {
                for (int number = 0; number<puzzle.length; number++){ 
                       possibilities[row][column][number] = true;   
                }                     
            }
        }
    }
 
    public static void resetPossibilitiesValue(int row, int column, int number) { 
 
                     resetRow( row, number);
                     resetColumn( column, number);
                     int rebox=getBox(row,column);
                     resetBox( rebox, number);
 
 
    }
 
    /**
     * Looks into the possibilities matrix and if the cell can have only one
     * possible value, then returns the correct number from 1 to 9,
     * else returns -1
     */
    public static void getCellSolution(int row, int column) {   
       int trues = 0,value = 0;
       for (int number = 0;number<9;number++) {
           if (possibilities[row][column][number]) {
                    trues++;  
                    value = number +1;
           }
       }
       if (trues == 1) {
                    puzzle[row][column] = value; 
                } 
       }     
    /**
     * Prints the Sudoku as 9 rows of 9 columns each
     */
    public static void printSudoku() {
       for( int row=0; row<puzzle.length; row++) { 
           for( int column=0; column<puzzle.length; column++) {
                    System.out.print(puzzle[row][column] + " ");
           }
            System.out.println(" ");
       }
    }
 
    public static void resetRow(int rerow, int number) {
         for( int column=0; column<puzzle.length; column++) {
                    possibilities[rerow][column][number-1] = false;
               }
    }
 
    public static void resetColumn(int recolumn, int number) {
          for(int row=0; row<puzzle.length; row++) {
                    possibilities[row][recolumn][number-1] = false;
          }
    }
 
    public static void resetBox(int box, int number) {
      switch(box) {
            case 1: for ( int row = 0; row<3; row++) {
                      for (int column= 0; column<3; column++) {
                           possibilities[row][column][number-1] = false;
                      }
                    } break;
            case 2: for ( int row = 0; row<3; row++) {
                      for (int column= 3; column<6; column++) {
                          possibilities[row][column][number-1] = false;  
                      }
                    } break;
            case 3: for ( int row = 0; row<3; row++) {
                      for (int column= 6; column<9; column++) {
                          possibilities[row][column][number-1] = false;  
                      }
                    }  break;
            case 4: for ( int row = 3; row<6; row++) {
                      for (int column= 0; column<3; column++) {
                          possibilities[row][column][number-1] = false;  
                      }
                    } break;
            case 5: for (int  row = 3; row<6; row++) {
                      for (int column= 3; column<6; column++) {
                          possibilities[row][column][number-1] = false;  
                      }
                    } break;
            case 6: for ( int row = 3; row<6; row++) {
                      for (int column= 6; column<9; column++) {
                          possibilities[row][column][number-1] = false;  
                      }
                    } break;
            case 7: for ( int row = 6; row<9; row++) {
                      for (int column= 0; column<3; column++) {
                          possibilities[row][column][number-1] = false;
                      }
                    } break;
            case 8: for ( int row = 6; row<9; row++) {
                      for (int column= 3; column<6; column++) {
                          possibilities[row][column][number-1] = false;
                      }
                    } break;
            case 9: for ( int row = 6; row<9; row++) {
                      for (int column= 6; column<9; column++) {
                          possibilities[row][column][number-1] = false; 
                      }
                    } break;
      }
    }
 
    public static int checkSudoku() {
        int count = 0;
        for(int row = 0; row< 9; row++) {
            for ( int column = 0; column<9; column++) {
               if (puzzle[row][column] != 0) {
                  count++;
               }
            }  
        } 
        return count;
    }         
     static int getBox(int row, int column) {
        int box = 0;
        box= ( 3*row/3)+(column/3) +1;
        return box; 
     }
 
 
    public static void main(String argv[]) {
        int row,column,number;
        fillPossibilitiesMatrix();
       while (checkSudoku() < 81) {
         for ( row=0; row<puzzle.length; row++) {
           for ( column=0; column<puzzle.length;column++)  {
             number =  puzzle[row][column];
             if(number != 0) {
                 resetPossibilitiesValue (row,column,number);
             } 
             else {
                 getCellSolution( row, column);
             }      
           }
         } 
        }
       printSudoku();    
    }  
    }

[JosAH]

Hi, did your program solve that puzzle? The solver described in that article solved
it instantaneously (I didn't time it though).

kind regards,

Jos