1 class Solution {
2 public:
3 bool solveSudoku(vector<vector<char> > & board, vector<vector<vector<bool> > > & flag, int x, int y){
4 bool wEnd = (x == 8 && y == 8) ? true: false;
5 int nextX = y<8? x: x+1;
6 int nextY = y<8? y+1: 0;
7 if (board[x][y]!='.'){
8 if (wEnd)
9 return true;
10 else return (solveSudoku(board, flag, nextX, nextY));
11 }
12 for (int i=0; i<9; i++){
13 int i1 = x;
14 int i2 = y;
15 int i3 = (x/3)*3 + y/3;
16 if (flag[0][i1][i] || flag[1][i2][i] || flag[2][i3][i])
17 continue;
18 board[x][y] = '1'+ i;
19 flag[0][i1][i] = flag[1][i2][i] = flag[2][i3][i] = true;
20 if (wEnd)
21 return true;
22 else if (solveSudoku(board, flag, nextX, nextY))
23 return true;
24 flag[0][i1][i] = flag[1][i2][i] = flag[2][i3][i] = false;
25 board[x][y] = '.';
26 }
27 return false;
28 }
29 void solveSudoku(vector<vector<char> > &board) {
30 vector<bool> vb(9,false);
31 vector<vector<bool> > vvb (9, vb);
32 vector<vector<vector<bool> > > flag(3, vvb);
33 for (int i=0; i<9; i++)
34 for (int j=0; j<9; j++){
35 int i1 = i;
36 int i2 = j;
37 int i3 = (i/3)*3 + j/3;
38 if (board[i][j] != '.'){
39 int index = board[i][j] - '1';
40 flag[0][i1][index] = flag[1][i2][index] = flag[2][i3][index] = true;
41 }
42 }
43 solveSudoku(board, flag, 0, 0);
44 }
45 };
