class Solution {
    public boolean isValidSudoku(char[][] board) {
        boolean case1=true, case2=true, case3=true;
        Set<Character> set1 = new HashSet<>();
        Set<Character> set2 = new HashSet<>();
        Set<Character> set3 = new HashSet<>();
        for(int i=0; i<9; i++){ 
            for(int j=0; j<9; j++){ 
                if(board[i][j] != '.' && !set1.add(board[i][j])) return false;
                if(board[j][i] != '.' && !set2.add(board[j][i])) return false;
                if(board[3*(i/3)+j/3][3*(i%3)+j%3] != '.' && 
                   !set3.add(board[3*(i/3)+j/3][3*(i%3)+j%3])) return false;
            }
            set1 = new HashSet<>();
            set2 = new HashSet<>();
            set3 = new HashSet<>();
        }
        return true;
    }
}