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  • Category: Programming

    Write a C program to solve Sudoku


    Searching for a program to solve Sodoku? On this Ask Expert page you find a solution to your queries.

    There are different versions of Sudoku. Some of them are:
    1) 4 x 4 (filled with 1, 2, 3, 4)
    2) 6 x 6 (filled with 1, 2, 3, 4, 5, 6)
    3) 8 x 8 (filled with 1, 2, 3, 4, 5, 6, 7, 8)
    4) 9 x 9 (filled with 1, 2, 3, 4, 5, 6, 7, 8, 9)
    5) 10 x 10 (filled with 1, 2, 3, 4, 5, 6, 7, 8, 9, a)
    Can anybody provide a C (or C++) menu driven program to solve all these types of Sudoku.
    Awaiting Response.
  • #137408
    You can use switch case to create a menu with multiple options and create separate functions for each option.

    Here is a example program to solve a 9x9 Sudoku. You can change the size of Sudoku according to your requirement.


    /*
    The program uses backtracking approach to solve the sudoku. There is a recursive function to solve the sudoku.
    */
    #include
    int sudoku[9][9];//The array which stores entries for the sudoku
    void solvesudoku(int,int);
    int checkrow(int row,int num)
    {//This function checks whether we can put the number(num) in the row(row) of the Sudoku or not
    int column;
    for(column=0;column<9;column++)
    if(sudoku[row][column]==num)
    return 0 ;//If the number is found already present at certain location we return zero
    return 1;//If the number is not found anywhere we return 1
    }
    int checkcolumn(int column,int num)
    {//This function checks whether we can put the number(num) in the column(column) of the Sudoku or not
    int row;
    for(row=0;row<9;row++)
    if(sudoku[row][column]==num)
    return 0;//If the number is found already present at certain location we return zero
    return 1;//If the number is not found anywhere we return 1
    }
    int checkgrid(int row,int column,int num)
    {//This function checks whether we can put the number(num) in the 3*3 grid or not
    //We get the starting row and column for the 3*3 grid
    row=(row/3)*3 ;
    column=(column/3)*3;
    int r,c;
    for(r=0;r<3;r++)
    for(c=0;c<3;c++)
    if(sudoku[row+r][column+c]==num)
    return 0;//If the number is found already present at certain location we return zero
    return 1;//If the number is not found anywhere we return 1
    }
    void navigate(int row,int column)
    {//Function to move to the next cell in case we have filled one cell
    if(column<8)
    solvesudoku(row,column+1);
    else
    solvesudoku(row+1,0);
    }
    void display()
    {//The function to display the solved Sudoku
    int row,column;
    printf("THE SOLVED SUDOKU \n");
    for(row=0;row<9;row++)
    {
    for(column=0;column<9;column++)
    printf("%d ",sudoku[row][column]);
    printf("\n");
    }
    getch();
    }
    void solvesudoku(int row,int column)
    {
    if(row>8)//If the row number is greater than 8 than we have filled all cells hence we have solved the sudoku
    display();
    if(sudoku[row][column]!=0)
    navigate(row,column);//If the value filled at a cell is not zero than it is filled with some value from 0 to 9 hence we move further
    else
    {
    int ctr;//This is a counter to check numbers from 1 to 9 whether the number can be filled in the cell or not
    for(ctr=1;ctr<=9;ctr++)
    {//We check row,column and the grid
    if((checkrow(row,ctr)==1)&&(checkcolumn(column,ctr)==1)&&(checkgrid(row,column,ctr)==1))
    {
    sudoku[row][column]=ctr;
    navigate(row,column);
    }
    }
    sudoku[row][column]=0;//No valid number was found so we clean up and return to the caller.
    }

    }
    int main()
    {
    int row,column;
    printf("Enter the desired sudoku and enter 0 for unknown entries\n");
    for(row=0;row<9;row++)
    for(column=0;column<9;column++)
    scanf("%d",&sudoku[row][column]);
    solvesudoku(0,0);//We start solving the sudoku.
    }

    Regards,

    VIVEK VAISHNAV


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