36. Valid Sudoku
Determine if a 9 x 9
Sudoku board is valid. Only the filled cells need to be validated according to the following rules:
- Each row must contain the digits
1-9
without repetition. - Each column must contain the digits
1-9
without repetition. - Each of the nine
3 x 3
sub-boxes of the grid must contain the digits1-9
without repetition.
Note:
- A Sudoku board (partially filled) could be valid but is not necessarily solvable.
- Only the filled cells need to be validated according to the mentioned rules.
Example 1:
Input: board = [["5","3",".",".","7",".",".",".","."] ,["6",".",".","1","9","5",".",".","."] ,[".","9","8",".",".",".",".","6","."] ,["8",".",".",".","6",".",".",".","3"] ,["4",".",".","8",".","3",".",".","1"] ,["7",".",".",".","2",".",".",".","6"] ,[".","6",".",".",".",".","2","8","."] ,[".",".",".","4","1","9",".",".","5"] ,[".",".",".",".","8",".",".","7","9"]] Output: true
Example 2:
Input: board = [["8","3",".",".","7",".",".",".","."] ,["6",".",".","1","9","5",".",".","."] ,[".","9","8",".",".",".",".","6","."] ,["8",".",".",".","6",".",".",".","3"] ,["4",".",".","8",".","3",".",".","1"] ,["7",".",".",".","2",".",".",".","6"] ,[".","6",".",".",".",".","2","8","."] ,[".",".",".","4","1","9",".",".","5"] ,[".",".",".",".","8",".",".","7","9"]] Output: false Explanation: Same as Example 1, except with the 5 in the top left corner being modified to 8. Since there are two 8's in the top left 3x3 sub-box, it is invalid.
Constraints:
board.length == 9
board[i].length == 9
board[i][j]
is a digit1-9
or'.'
.
solution:
class Solution {
public:
bool isValidSudoku(vector<vector<char>>& board) {
unordered_set<string>map;
for(int i = 0; i <9 ; i++ )
{
for(int j =0 ; j < 9 ; j++)
{
int box = (i/3)*3 + (j/3);
if(board[i][j] != '.')
{
string s = "row";
string t = "col";
string u = "box";
char a = i+'0';
char b = j +'0';
char c = box +'0';
s = s+a+ board[i][j];
t = t+b+ board[i][j];
u = u+c+ board[i][j];
if(map.find(s) == map.end())
map.insert(s);
else
return false;
if(map.find(t) == map.end())
map.insert(t);
else
return false;
if(map.find(u) == map.end())
map.insert(u);
else
return false;
}
}
}
return true;
}
};
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