Valid Sudoku

Q:
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.

A:   就是道简单的实现题

public class Solution {
    public boolean isValidSudoku(char[][] board) {
        // if(board==null || board.length ==0 || board.length !=9 || board[0].length!=9)
        //     return false;
        for(int i =0;i<board.length;i++){
            for(int j =0;j< board[0].length;j++)
                if( !isValid(i,j,board))
                    return false;
        }
        return true;
    }
    private boolean isValid(int row, int col , char[][] board){
        char ch = board[row][col];
        if(ch == '.')
            return true;
        for(int i = row+1; i<board.length;i++)
            if(board[i][col] == ch)
                return false;
        for(int j = col+1;j<board[0].length;j++)
            if(board[row][j] == ch)
                return false;
        board[row][col] = '.';// temporaryly change it 
        for(int i = 0;i<3;i++)
            for(int j = 0;j<3;j++)
                if(board[row/3 * 3 +i][col/3*3+j] == ch)
                    return false;
        board[row][col]=ch;
        return true;
    }
}

这里，在小方框里，忘记check是否是原来的位置。

public class ValidSudoku {
    public boolean isValidSudoku(char[][] board) {
        // we only check valid, but not solvable
        if(board==null || board.length ==0 || board.length !=9 || board[0].length!=9){
            return false;
        }

        // check valid row   & check valid chars
        boolean[] validArray;
        for (int i = 0; i < 9; i++) { // for each row
            validArray = new boolean[10];
            for (int j = 0; j < 9; j++) {
                // check valid of chars
                if (! (board[i][j] >= '0' && board[i][j] <= '9')
                        &&  board[i][j] != '.') {
                    return false;
                }
                if(board[i][j]=='.')continue;
                int value = Integer.valueOf("" + board[i][j]);
                if (validArray[value]) {
                    return false;
                } else {
                    validArray[value] = true;
                }
            }
        }
        // check valid col
        for (int j = 0; j < 9; j++) {
            validArray = new boolean[10];
            for (int i = 0; i < 9; i++) { // for each row
                if(board[i][j]=='.')continue;
                int value = Integer.valueOf("" + board[i][j]);
                if (validArray[value]) {
                    return false;
                } else {
                    validArray[value] = true;
                }
            }
        }
        // check valid square
        for (int outerI = 0; outerI < 3; outerI++) {
            for (int outerJ = 0; outerJ < 3; outerJ++) {
                validArray = new boolean[10];
                for (int i = 0; i < 3; i++) {
                    for (int j = 0; j < 3; j++) {
                        if(board[3*outerI+i][3*outerJ+j]=='.')continue;
                        int value = Integer.valueOf("" + board[3*outerI+i][3*outerJ+j]);
                        if (validArray[value]) {
                            return false;
                        } else {
                            validArray[value] = true;
                        }
                    }
                }
            }
        }
        return true;
    }
}

Mistakes:
1： 对每个board上的数字， 当转换到int类型的时候，忘了检查，是否为'.'   ， 造成了 Exception
2： 在检查小方格的时候， 忘了算上outerI，  outerJ的基数， 哎， SB啊
int value = Integer.valueOf("" + board[3*outerI+i][3*outerJ+j]);


Learned: