每日算法题：19.7.17

题目：

判断一个 9x9 的数独是否有效。只需要根据以下规则，验证已经填入的数字是否有效即可。

    数字 1-9 在每一行只能出现一次。
    数字 1-9 在每一列只能出现一次。
    数字 1-9 在每一个以粗实线分隔的 3x3 宫内只能出现一次。

    数独部分空格内已填入了数字，空白格用 '.' 表示。

示例：

输入:
[
  ["5","3",".",".","7",".",".",".","."],
  ["6",".",".","1","9","5",".",".","."],
  [".","9","8",".",".",".",".","6","."],
  ["8",".",".",".","6",".",".",".","3"],
  ["4",".",".","8",".","3",".",".","1"],
  ["7",".",".",".","2",".",".",".","6"],
  [".","6",".",".",".",".","2","8","."],
  [".",".",".","4","1","9",".",".","5"],
  [".",".",".",".","8",".",".","7","9"]
]
输出: true

代码：

public class Test12 {
    @Test
    public void test(){
        char[][] test = new char[][]{{'5','3','.','.','7','.','.','.','.'},
                {'6','.','.','1','9','5','.','.','.'},{'.','9','8','.','.','.','.','6','.'},
                {'8','.','.','.','6','.','.','.','3'},{'4','.','.','8','.','3','.','.','1'},
                {'7','.','.','.','2','.','.','.','6'},{'.','6','.','.','.','.','2','8','.'},
                {'.','.','.','4','1','9','.','.','5'},{'.','.','.','.','8','.','.','7','9'}};
        boolean validSudoku = new Test12().isValidSudoku(test);
        System.out.println(validSudoku);

    }
    public boolean isValidSudoku(char[][] board) {
        for (int i = 0; i < board.length; i++) {
            for (int j = 0; j < board[i].length; j++) {
                char stand = board[i][j];

                if (stand=='.') {
                    continue;
                }

                for (int k = 0; k < board[i].length; k++) {
                    if (k==j) {
                        continue;
                    }
                    if ((board[i][k])==stand) {
                        return false;
                    }
                }

                for (int k = 0; k < board.length; k++) {
                    if (k==i) {
                        continue;
                    }
                    if ((board[k][j])==stand) {
                        return false;
                    }
                }

                int lineIndex = i-i%3;
                int columnIndex = j-j%3;
                for (int k = lineIndex; k < lineIndex+3; k++) {
                    for (int l = columnIndex; l < columnIndex+3 ; l++) {
                        if (k==i&&l==j) {
                            continue;
                        }
                        if ((board[k][l])==stand) {
                            return false;
                        }
                    }
                }
            }
        }

        return true;
    }
}