Day 7 - Solution

class Solution {
    
    public boolean areRowsValid(char[][] board, Set<Character> set){
        for(int i=0;i<9;i++){
            set.clear();
            for(int j=0;j<9;j++){
                if(set.contains(board[i][j])) 
                    return false;
                if(board[i][j]!='.') 
                    set.add(board[i][j]);
            }
        }
        return true;
    }
    
    public boolean areColsValid(char[][] board, Set<Character> set){
        for(int i=0;i<9;i++){
            set.clear();
            for(int j=0;j<9;j++){
                if(set.contains(board[j][i])) 
                    return false;
                if(board[j][i]!='.') 
                    set.add(board[j][i]);
            }
        }
        return true;
    }
    
    public boolean areBoxesValid(char[][] board, Set<Character> set){
        for(int m=0;m<9;m+=3){
            for(int n=0;n<9;n+=3){
                set.clear();
                for(int i=0;i<3;i++){
                    for(int j=0;j<3;j++){
                        if(set.contains(board[i+m][j+n])) 
                            return false;
                        else if(board[i+m][j+n]!='.') 
                            set.add(board[i+m][j+n]);
                    }
                }
            }
        }
        return true;
    }
    
    public boolean isValidSudoku(char[][] board) {
        Set<Character> set = new HashSet<>();
        
        return areRowsValid(board, set) &&
            areColsValid(board,set) &&
            areBoxesValid(board,set);
    }
}