36 Valid Sudoku

LeetCode 36 Valid Sudoku

Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

• Each row must contain the digits 1-9 without repetition.
• Each column must contain the digits 1-9 without repetition.
• Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition.

Note:

• A Sudoku board (partially filled) could be valid but is not necessarily solvable.
• Only the filled cells need to be validated according to the mentioned rules.

class Solution {
    public boolean isValidSudoku(char[][] board) {
        for(int i=0;i<9;++i){
            if(!(isRowValid(board,i) && isColValid(board,i))) return false;
        }
        
        for(int i=0;i<9;i=i+3){
            for(int j=0;j<9;j=j+3){
                if(!isBlockValid(board,i,j)) return false;
            }
        }
        return true;
    }
    
    private boolean isRowValid(char[][] board, int row){
        boolean[] arr=new boolean[9];
        for(int j=0;j<9;++j){
            char c = board[row][j];
            if(c>='1' && c<='9'){
                int val = c-'1';
                if(arr[val]) return false;
                arr[val] = true;
            }
        }
        return true;
    }
    
    private boolean isColValid(char[][] board, int col){
        boolean[] arr=new boolean[9];
        for(int i=0;i<9;++i){
            char c = board[i][col];
            if(c>='1' && c<='9'){
                int val = c-'1';
                if(arr[val]) return false;
                arr[val] = true;
            }
        }
        return true;
    }
    
    private boolean isBlockValid(char[][] board, int i, int j){
        int row=i/3*3;
        int col=j/3*3;
        boolean[] arr=new boolean[9];
        for(int ii=0;ii<3;ii++){
            for(int jj=0;jj<3;jj++){
                char c=board[row+ii][col+jj];
                if(c>='1' && c<='9'){
                    int val = c-'1';
                    if(arr[val]) return false;
                    arr[val] = true;
                }
            }
        }
        return true;         
    }
}