leetcode - Valid Sudoku

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.

The Sudoku board could be partially filled, where empty cells are filled with the character

'.'

.



A partially filled sudoku which is valid.

Note:

A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.

class Solution {
public:
bool isValidSudoku(std::vector<std::vector<char> > &board) {
int rows = board.size();
int cols = board[0].size();
int mask=0;
int val;
for(int i=0;i<rows;i++){
mask=0;
for(int j=0;j<cols;j++){
if(board[i][j]!='.'){
int val = (int)(board[i][j]-'0');
if(mask & (1<<val))
return false;
else mask |= (1<<val);
}
}
}
//rows are checked
for(int j=0;j<cols;j++){
mask=0;
for(int i=0;i<rows;i++){
if(board[i][j]!='.'){
int val = (int)(board[i][j]-'0');
if(mask & (1<<val))
return false;
else mask |= (1<<val);
}
}
}
//cols are checked
for(int i=0;i<rows;i+=3)
{
for(int j=0;j<cols;j+=3)
{
mask=0;
for(int k=i;k<=i+2;k++)
{
for(int l=j;l<=j+2;l++)
{
if(board[k][l]!='.'){
val = (int)(board[k][l]-'0');
if(mask&(1<<val))
return false;
else mask|=(1<<val);
}
}
}
}
}
return true;
}
};