Class Solution

C++/Sudoku-Solver.cpp:7–108

* Runtime - 56ms * Memory - 6.8 * LOGIC - described in functions * */

 * 
 */
class Solution {
public:

	// to check whether num is valid in that row    
    bool isRowSafe(vector<vector<char>>& board, int row, char  num)
    {
        for(int col = 0;col<9;col++)
        {
            if(board[row][col] == num)
                return true;
        }
        return false;
    }
    
    // to check whether num is valid in that column
    bool isColumnSafe(vector<vector<char>>& board, int col , char  num)
    {
         for(int row = 0; row<9; row++)
        {
            if(board[row][col] == num)
                return true;
        }
        return false;
    }
    
    // to check whether num is valid in that 3*3 matrix grid 
    bool isBoxSafe(vector<vector<char>>& board, int row1, int col1 , char  num)
    {
         for(int row = 0;row<3;row++)
            {
                for(int col = 0;col<3;col++)
                    {
                         if(board[row1 + row][col1 + col] == num)
                            return true;
                    }
            }
        
        return false;
    }
    
    bool isSafe(vector<vector<char>>& board, int row, int col , char  num)
    {
        return !isRowSafe(board,row,num) && !isColumnSafe(board, col, num) && !isBoxSafe(board, row-row%3,col-col%3,num) && board[row][col] == '.';
    }
    
    
    bool findUnassignedLocation(vector<vector<char>>& board, int &row, int &col)
    {
        for(row = 0;row<9;row++)
            {
                for(col = 0;col<9;col++)
                    {
                        if(board[row][col] == '.')
                            return true;
                    
                }
        }
        return false;