36.txt

class Solution {
    public boolean isValidSudoku(char[][] board) {
        HashSet<Character> row = new HashSet();
        HashSet<Character> column = new HashSet();
        HashSet<Character> grid = new HashSet();
        for (int i = 0; i < 9; i++) {
            for (int j = 0; j < 9; j++) {
                if(board[i][j] != '.') {
                        if(!row.add(board[i][j]))
                            return false;
                }
                if(board[j][i] != '.') {
                    if(!column.add(board[j][i]))
                        return false;
                }
                int RowIndex = 3*(i/3);
                int ColIndex = 3*(i%3);
                if(board[RowIndex + j/3][ColIndex + j%3]!='.' && !grid.add(board[RowIndex + j/3][ColIndex + j%3]))
                    return false;
            }
            row.clear();
            column.clear();
            grid.clear();
        }
        return true;
    }
}