Sudoku Solver

Write a program to solve a Sudoku puzzle by filling the empty cells.

Empty cells are indicated by the character 

'.'

.

You may assume that there will be only one unique solution.



A sudoku puzzle...



...and its solution numbers marked in red.
解：

bool isValid(vector<vector<char>> & board, int x, int y){
for(int i=0; i<board.size(); i++){
if(board[i][y]=='.' || i==x)
continue;
if(board[x][y]==board[i][y])
return false;
}

for(int i=0; i<board[0].size(); i++){
if(board[x][i]=='.' || i==y)
continue;
if(board[x][y]==board[x][i])
return false;
}

int startx=x/3*3;
int starty=y/3*3;
for(int i=startx; i<startx+3; i++){
for(int j=starty; j<starty+3; j++){
if(board[i][j]=='.' || i==x || j==y)
continue;
if(board[i][j]==board[x][y])
return false;
}
}
return true;
}

bool solveSudo(vector<vector<char>>& board) {
for(int i=0; i<board.size(); i++){
for(int j=0; j<board[0].size(); j++){
if(board[i][j]!='.')
continue;
int k;
for(k=1; k<10; k++){
board[i][j]=k+'0';
if(isValid(board, i, j))
{
if(solveSudo(board))
return true;
}
board[i][j]='.';
}
return false;//没有任何判断，直接返回false
}
}
return true;
}

void solveSudoku(vector<vector<char>>& board) {
solveSudo(board);
}