[LeetCode]036. Valid Sudoku

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.

The Sudoku board could be partially filled, where empty cells are filled with the character '.'.

A partially filled sudoku which is valid.

Solution: use the int[] row, col, squ store the occurence of digit in the row, col, and 3*3 square

must note to reinitialize the three int[] after each one loop.

public class Solution {
    public boolean isValidSudoku(char[][] board) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(board==null || board.length!=9 || board[0].length!=9){
            return false;
        }
        for(int i=0; i<9; i++){
            //the hash array must be reinitialized
            int[] row = new int[9];
            int[] col = new int[9];
            for(int j=0; j<9; j++){
                //check duplicates in each row
                if(board[i][j] != '.'){
                    int m = board[i][j]-'1';
                    if(row[m]==1){
                        return false;
                    }else{
                        row[m]++;
                    }
                }
                //check duplicates in each column
                if(board[j][i] != '.'){
                    int n =board[j][i] - '1';
                    if(col[n]==1){
                        return false;
                    }else{
                        col[n]++;
                    }
                }
            }
        }
        
        //check the duplicates in 3*3 square
        for(int i=0; i<9; i+=3){
            for(int j=0; j<9; j+=3){
                //the hash array must be reinitialized
                int[] squ = new int[9];
                for(int m=0; m<3; m++){
                    for(int n=0; n<3; n++){
                        if(board[i+m][j+n] == '.'){
                            continue;
                        }else{
                            int x = board[i+m][j+n] - '1';
                            if(squ[x] == 1){
                                return false;
                            }else{
                                squ[x]++;
                            }
                        }
                    }
                }
            }
        }
        return true;
    }
}