# Valid Sudoku

Valid Sudoku hash table

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules. (http:sudoku.com.au/TheRules.aspx) 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.

Valid Sudoku Solution

``````class ValidSudoku {
public boolean isValidSudoku(char[][] board) {
for(int i = 0; i < board.length; i++){
HashSet<Character> rows = new HashSet<Character>();
HashSet<Character> columns = new HashSet<Character>();
HashSet<Character> box = new HashSet<Character>();
for (int j = 0; j < board[0].length; j++){
if(board[i][j] != '.' && !rows.add(board[i][j])) {
return false;
}
if(board[j][i]!='.' && !columns.add(board[j][i])) {
return false;
}
int rowIndex = (i / 3) * 3;
int columnIndex = (i % 3) * 3;
if(board[rowIndex + j / 3][columnIndex + j % 3] != '.' && !box.add(board[rowIndex + j / 3][columnIndex + j % 3])) {
return false;
}
}
}
return true;
}
}``````