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Determine if a 9x9 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 9
3x3
sub-boxes of the grid must contain the digits1-9
without repetition.
A partially filled sudoku which is valid.
The Sudoku board could be partially filled, where empty cells are filled with the character '.'
.
Example 1:
Input: [ ["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: [ ["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.
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.
- The given board contain only digits
1-9
and the character'.'
. - The given board size is always
9x9
.
哈希表实现,分别判断行,列,与9个3*3小格
class Solution {
public:
bool isValidSudoku(vector<vector<char>>& board) {
unordered_map<char,int> hash;
//row
for(int i=0;i<9;i++)
{
for(int j=0;j<9;j++)
{
if(board[i][j]=='.')
continue;
if(hash.find(board[i][j])==hash.end())
{
hash[board[i][j]]++;
continue;
}
return false;
}
hash.clear();
}
hash.clear();
//col
for(int i=0;i<9;i++)
{
for(int j=0;j<9;j++)
{
if(board[j][i]=='.')
continue;
if(hash.find(board[j][i])==hash.end())
{
hash[board[j][i]]++;
continue;
}
return false;
}
hash.clear();
}
hash.clear();
//3*3cube
for(int i=0;i<9;i++)
{
//注意逐个取3*3小格的取法,行:3*(i/3)--3+3*(i/3),列:3*(i%3)--3+3*(i%3)
for(int j=3*(i/3);j<3+3*(i/3);j++)
{
for(int k=3*(i%3);k<3+3*(i%3);k++)
{
if(board[j][k]=='.')
continue;
if(hash.find(board[j][k])==hash.end())
{
hash[board[j][k]]++;
continue;
}
return false;
}
}
hash.clear();
}
return true;
}
};