Valid Sudoku

Valid Sudoku

问题：

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 '.'.

思路：

　　简单的数学运算

我的代码：

public class Solution {

    public boolean isValidSudoku(char[][] board) {

        if(board == null || board.length == 0 || board[0].length == 0)  return true;

        int row = board.length;

        int col = board[0].length;

        for(int i = 0; i < row; i++)

        {

            for(int j = 0; j < col; j++)

            {

                char c = board[i][j];

                if(c == '.')    continue;

                else

                {

                    //test row

                    for(int k = 0; k < j; k++)

                    {

                        if(board[i][k] == c)    return false;

                    }

                    //test col

                    for(int k = 0; k < i; k++)

                    {

                        if(board[k][j] == c)  return false;

                    }

                    //test box

                    int boxRow = i/3;

                    int boxCol = j/3;

                    for(int m = boxRow * 3; m < boxRow * 3 + 3; m++)

                    {

                        for(int n = boxCol * 3; n < boxCol * 3 + 3; n++)

                        {

                            if(board[m][n] == '.' || (m == i && n == j))  continue;

                            else

                            {

                                if(board[m][n] == c)    return false;

                            }

                        }

                    }

                }

            }

            

        }

        return true;

    }

}

View Code

他人代码：

public boolean isValidSudoku(char[][] board) {

        // Start typing your Java solution below

        // DO NOT write main() function

       

        for(int i=0; i<board.length; i++){

            for(int j=0; j<board[0].length; j++){

                if(board[i][j]=='.')

                    continue;

                char tmp = board[i][j];

                board[i][j] = 'C';

                boolean tr = isValid(board, i, j, tmp);

                board[i][j] = tmp;

                if(tr == false)

                    return tr;

            }

        }

        return true;

    }

   

    public boolean isValid(char[][] board, int x, int y, char tmp){

        for(int i=0; i<9; i++){

            if(board[x][i] == tmp || board[i][y] == tmp)

                return false;

        }

       

        int start_x = x/3;

        int start_y = y/3;

        for(int i=0; i<9; i++){

            int cur_x = start_x*3 + i/3;

            int cur_y = start_y*3 + i%3;

            if(board[cur_x][cur_y] == tmp)

                return false;

        }

        return true;

    }

View Code

学习之处：

• 测试了好多次才过 不能忍 错误之处是 start = i/3 end = i/3 + 3 正确应该是 start = i/3 * 3 end = i/3 * 3 + 3 忘记 * 3 + 3了
• 他人的代码用9 一次访问一行或者一列或者一个box，代码简单易行