题目链接：

因为我也还没有完全理解这道题，所以不能写出详细的解答过程以及理解的思路。就先贴代码吧！

代码：

public void solveSudoku(char[][] board) {        search(board);    }    private boolean search(char[][] board){        for (int i = 0; i < board.length; i++){            for (int j = 0; j < board[0].length; j++){                if (board[i][j] != '.')  // 只有是 .号，也就是空格，我们才能填充数据                    continue;                for (char ch = '1'; ch <= '9'; ch++){  // 在board[i][j]中填充 0~9 来测试填入数据后board是否还是一个数独                    if (!isValid(board, i, j, ch)){                        continue;                    }                    board[i][j] = ch;                    if (search(board)){                        return true;                    }else {                        board[i][j] = '.';                    }                }                return false;            }        }        return true;    }    private boolean isValid(char[][] board, int i, int j, char ch) {        // 行不重复        for (int col = 0; col < 9; col++){            if (board[i][col] == ch){                return false;            }        }        // 列不重复        for (int row = 0; row < 9; row++){            if (board[row][j] == ch){                return false;            }        }        // 3 X 3的小方格不重复        for (int row = i / 3 * 3; row < i / 3 * 3 + 3; row++){            for (int col = j / 3 * 3; col < j / 3 * 3 + 3; col++){                if (board[row][col] == ch){                    return false;                }            }        }        return true;    }