Sudoku is a puzzle involving a 9× 9 grid with 9 3× 3 subgrids. A correct solutio

Question

Sudoku is a puzzle involving a 9× 9 grid with 9 3× 3 subgrids. A correct solution for a puzzle instance requires that each subgrid, row and column in the 9 × 9 grid has each of the digits from 1 to 9, The algo- rithm checkGrid checks if a given table is a correct sudoku solution. Re-write the algorithm checkGrid using modules. You must write algorithms for each module that is used by the new version of the algo- rithm. checkGrid(S 0.8,0.8 Input: A candidate solution, S, represented as a 9 × 9 table Output: True if the table represents a valid solution, otherwise False while(r

Explanation / Answer

#include <iostream.h>

#include <fstream>

using namespace std;

void readpuzzle ( int grid[][9]);

bool isValid(int p, int q, int grid[][9]);

bool isValid(int grid[][9]);

void printGrid(int grid[] [9]);

int main()

{

int grid [9][9];

readpuzzle (grid);

if (!isValid(grid))

cout << " Invalid Input " << endl;

else if ()

printGrid(grid);

else

cout << " not a solution " << endl;

return EXIT_SUCCESS;

}

void readpuzzle (int grid[][9])

{

{

// check

cout << "Enter puzzle of sudoku:" << endl;

for (int p = 0; p < 9; p++)

for (int q = 0; q < 9; q++)

cin >> grid[p] [q];

}

}

bool isValid(int p, int q, int grid[] [9])

{
// Check the grid[p][q] is valid or not at p's row

for (int col = 0; col < 9; col++)

if (col != q && grid[p] [col] == grid[p] [q])

return false;

// Check the grid[p][q] is valid or not at the q's column

for (int row = 0; row < 9; row++)

if (row != p && grid[row] [q] == grid[p] [q])

return false;

// Check the grid[p][q] is valid or not in the 3 by 3 box

for (int row = (p / 3) * 3; row < (q / 3) * 3 + 3; row++)

for (int col1 = (q / 3) * 3; co1l < (q / 3) * 3 + 3; col1++)

if ( grid[row] [col1] && row != p && col1 != q == grid[p] [q])

return false;

return true;

}

/** Check the fixed cells are valid or not in the grid */

bool isValid(int grid[][9]) {

// Check for the equal numbers

for (int p = 0; p< 9; p++)

for (int q = 0; q < 9; q++)

if (grid[p][q] != 0)

if (!isValid(p, q, grid))

return false;

// Check the numbers are in the range

for (int p = 0; p < 9; p++)

for (int q = 0; q < 9; q++)
if ((grid[p][q] < 0) || (grid[p][q] > 9))

return false;

return true; // The fixed cells values are valid

}

/* fix the values in the grid */

void printGrid(int grid[] [9])

{

for (int p = 0; p < 9; p++)

{

for (int q = 0; q < 9; q++)

cout << grid[p] [q] << " ";

cout << endl;

}

}

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