Sudoku Solver

 1 class Solution {
 2 public:
 3     void solveSudoku(vector<vector<char> > &board) {
 4         process(board, 0,0);
 5         
 6     }
 7     bool process(vector<vector<char>> &board,int i,int j)
 8     {
 9 
10         if(j==9)
11         {
12             return process(board,i+1,0);//!!!
13         }
14         if(i==9)
15         {
16             //cout<<"true";
17             return true;
18         }
19         if(board[i][j]==‘.‘)
20         {
21             for(int k=1;k<10;k++)
22             {
23 
24                 if(isValid(board,i,j,k))
25                 {
26                 board[i][j]=‘0‘+k;
27                 if(process(board,i,j+1)) {return true;}
28                 board[i][j]=‘.‘;
29                 }
30                 
31             }
32 
33             return false;
34         }
35         else return process(board,i,j+1);
36         
37     }
38     bool isValid(vector<vector<char>> &board,int i, int j, int k)
39     {
40         
41         char qq=‘0‘+k;
42         for(int m=0;m<9;m++)
43         {
44             if(board[i][m]==qq){return false;}
45         }
46         for(int m=0;m<9;m++)
47         {
48             if(board[m][j]==qq)return false;
49         }
50         int m=i/3, n=j/3;
51         for(int p=m*3;p<m*3+3;p++)
52         {
53             for(int q=n*3;q<n*3+3;q++)
54             {
55                 if(board[p][q]==qq)return false;
56             }
57         }
58         return true;
59     }
60 };