[leetcode]Valid Sudoku

class Solution {
public:
bool isValidSudoku(vector<vector<char> > &board) {
unordered_set<int> vis;
//valid row
for(int i = 0 ; i < 9 ; i++) { //enumerate row
vis.clear();
for(int j = 0 ; j < 9 ; j++) {
if(board[i][j] == '.')
continue;
else {
if(board[i][j] >= '1' && board[i][j] <= '9' && vis.find(board[i][j]) == vis.end()) {
vis.insert(board[i][j]);
} else {
return false;
}
}
}
}
//valid col
for(int i = 0 ; i < 9 ; i++) {
vis.clear();
for(int j = 0 ; j < 9 ; j++) {
//i col , j = row
if(board[j][i] == '.')
continue;
else {
if(board[j][i] >= '1' && board[j][i] <= '9' && vis.find(board[j][i]) == vis.end()){
vis.insert(board[j][i]);
} else {
return false;
}
}
}
}
//valid block
for(int i = 0 ; i < 9 ; i += 3) {
for(int j = 0 ; j < 9 ; j += 3) {
//block start
vis.clear();
for(int row = 0 ; row < 3 ; row ++) {
for(int col = 0 ; col < 3 ; col ++) {
if(board[i + row][j + col] == '.')
continue;
else {
if (board[i + row][j + col] >= '1' && board[i + row][j + col] <= '9' && vis.find(board[i + row][j + col]) == vis.end()) {
vis.insert(board[i + row][j + col]);
} else {
return false;
}
}
}
}
}
}
return true;
}
};