【leetcode】Sudoku Solver

 1 class Solution {
 2 public:
 3     
 4     bool isValid(vector<vector<char> > &board,int i0,int j0)
 5     {
 6         char target=board[i0][j0];
 7         
 8         for(int i=0;i<9;i++)
 9         {
10             if(i==i0) continue;
11             if(board[i][j0]==target)
12             {
13                 return false;
14             }
15         }
16         
17 
18         for(int j=0;j<9;j++)
19         {
20             if(j==j0) continue;
21             if(board[i0][j]==target)
22             {
23                 return false;
24             }
25         }
26 
27         for(int i=i0/3*3;i<i0/3*3+3;i++)
28         {
29             
30             for(int j=j0/3*3;j<j0/3*3+3;j++)
31             {
32                 if(i==i0&&j==j0) continue;
33                 if(board[i][j]==target)
34                 {
35                     return false;
36                 }
37             }
38         }
39         
40         return true;
41     }
42     
43     
44     bool scanPos(vector<vector<char> > &board,int pos)
45     {
46         if(pos==81) return true;
47         
48         
49         bool flag=false;
50         int i0=pos/9;
51         int j0=pos%9;
52         
53         if(board[i0][j0]!=‘.‘)
54         {
55             return scanPos(board,pos+1);
56         }
57         
58         for(int j=1;j<=9;j++)
59         {
60             
61             board[i0][j0]=‘0‘+j;
62             if(isValid(board,i0,j0))
63             {
64                 if(scanPos(board,pos+1))
65                 {
66                     flag=true;
67                     break;
68                 }
69             }
70         }
71         
72         if(flag==false)
73         {
74             board[i0][j0]=‘.‘;
75             return false;
76         }
77         else
78         {
79             return true;
80         }
81     }
82 
83 
84     void solveSudoku(vector<vector<char> > &board) {
85         scanPos(board,0);
86     }
87 };