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Thread: Need help with this Sudoku code.

  1. #1
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    Default Need help with this Sudoku code.

    I can run the code but it does not solve, I can not figure it out. Thx

    public class SudokuTestSolver {
    int Unassigned = 0;
     
     
    public boolean solveSudoku(int[][] grid) {
    	int x = 0;
    	int y = 0;
     
    	// If there is no unassigned location, we are done
    	if (!findUnassignedLocation(grid, x, y)) {
    	   return true;
    	}
     
    	for (int num = 1; num <= 9; num++) {
     
    		if (isSafe(grid, x, y, num)) {
     
    			grid[x][y] = num;
     
    			if (solveSudoku(grid)) {
    				return true;
    			}
     
    			grid[x][y] = Unassigned;
    		}
     
    	}
    	return false; 
    }
     
     
     
    public boolean findUnassignedLocation(int[][] grid, int x, int y) {
    	for (int i = 0; i < 9; i++) {
    		for (int j = 0; j < 9; j++) {
    			if (grid[x][y] == 0) {
    				return true;   
    			}
    		}
    	}
    	return false;
     
    }
     
    public boolean usedInRow(int[][] grid, int x, int num) {
    	for (int y = 0; y < 9; y++) {
    		if (grid[x][y] == num) {
    			return true;
    		}
    	}
    	return false;
    }
     
     
     
    public boolean usedInCol(int[][] grid, int y, int num) {
    	for (int x = 0; x < 9; x++) {
    		if (grid[x][y] == num) {
    			return true;
    		}
    	}
    	return false;
    }
     
     
    public boolean usedInBox(int[][] grid, int boxStartRow, int boxStartCol, int num) {
    	for (int x = 0; x < 3; x++) {
    		for (int y = 0; y < 3; y++) {
    			if (grid[x + boxStartRow * 3][y + boxStartCol * 3] == num) {
    				return true;
    			}
    		}
    	}
    	return false;
    }
     
     
     
    public boolean isSafe(int grid[][], int x, int y, int num) {
     
        return !usedInRow(grid, x, num) && 
               !usedInCol(grid, y, num) && 
               !usedInBox(grid, x - x%3 , y - y%3, num);
    }
     
     
    public void printGrid(int grid[][]) {
        for (int x = 0; x < 9; x++) {
           for (int y = 0; y < 9; y++)
              System.out.print(grid[x][y] + "  ");
            System.out.println();
        }
    }
     
     
    public static void main(String[] args) {
                  int grid[][] = {{3, 0, 0,  0, 0, 0,  0, 0, 0},
                                  {0, 0, 0,  0, 0, 0,  0, 0, 0},
                                  {0, 0, 0,  1, 0, 0,  0, 0, 0},
     
                                  {0, 0, 0,  0, 0, 0,  0, 0, 0},
                                  {0, 0, 0,  0, 0, 0,  0, 0, 0},
                                  {0, 0, 0,  0, 0, 0,  0, 0, 0},
     
                                  {0, 0, 0,  0, 0, 0,  2, 0, 0},
                                  {0, 0, 0,  0, 0, 0,  0, 0, 0},
                                  {0, 0, 0,  0, 0, 0,  0, 0, 0}};
     
    SudokuTestSolver s = new SudokuTestSolver();
     
     
     
    int grid2[][] = new int[9][9];
     
     
    for (int x = 0; x < 9; x++) {
       for (int y = 0; y < 9; y++) {
          grid2[x][y] = grid[x][y];
       }
    }
     
    if (s.solveSudoku(grid2) == true) {
     
       s.printGrid(grid2);
    }
    else {
       System.out.println("Can not be solved"); 
    }  
     
    }//end main
     
     
    }//end class

  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Need help with this Sudoku code.

    it does not solve
    Why do you think the code should be able to solve?

    If you think the code is designed to use a good algorithm, how are you trying to debug the code to see if it is following the design?
    If you don't understand my answer, don't ignore it, ask a question.

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