Leetcode--初级--数组--有效的数独

Leetcode–数组–有效的数独

题目 有效的数独

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。

上图是一个部分填充的有效的数独。

数独部分空格内已填入了数字，空白格用 ‘.’ 表示。

示例 1:

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
示例 2:

输入:
[
[“8”,”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: false
解释: 除了第一行的第一个数字从 5 改为 8 以外，空格内其他数字均与 示例1 相同。

但由于位于左上角的 3x3 宫内有两个 8 存在, 因此这个数独是无效的。

思路

1.判断一行中是否有重复元素
2.判断一列中是否有重复元素
3.判断一个3*3的块中是否有重复元素

以上思路太蠢，用3个矩阵分别记录 每一行，每一列，每一块的出现过的数字。对整个9*9的区域只循环一次。

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细节

1.使用enumerate循环，同时返回下标和数组元素
2.对于第i行，第j个元素，属于第k个块  k=(i/3)*3+j/3
3.向 row[i]中添加i行元素 column[j]中添加j列元素 block[k]中添加k块元素

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代码块

class Solution:
    def isValidSudoku(self, board):
        rows = [[] for i in range(9)]
        column = [[] for j in range(9)]
        block = [[] for k in range(9)]
        for i,row in enumerate(board):
            for j,num in enumerate(row):
                if num != '.':
                    k = (i//3)*3+j//3
                    if num in rows[i] or num in column[j] or num in block[k]:
                        print(i)
                        print(j)
                        print(k)
                        return False
                    else:
                        rows[i].append(num)
                        column[j].append(num)
                        block[k].append(num)
        return True

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