Question Definition
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.
Java Solution
public boolean isValidSudoku(char[][] board) {
Map<Character, List<Integer[]>> map = new HashMap<>();
for(int i = 0; i < board.length; i++){
for(int j = 0; j < board[i].length; j++){
char c = board[i][j];
if(c == '.') continue;
map.putIfAbsent(c, new LinkedList<>());
for(Integer[] point : map.get(c)){
if(point[0] == i || point[1] == j){
return false;
}
if((point[0] >= (i / 3) * 3 && point[0] < (i / 3 + 1) * 3)
&& (point[1] >= (j / 3) * 3 && point[1] < (j / 3 + 1) * 3)){
return false;
}
}
map.get(c).add(new Integer[]{i, j});
}
}
return true;
}
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