LeetCode Python 36 有效的數獨

判斷乙個 9x9 的數獨是否有效。只需要根據以下規則，驗證已經填入的數字是否有效即可。

數字1-9在每一行只能出現一次。

數字1-9在每一列只能出現一次。

數字1-9在每乙個以粗實線分隔的3x3宮內只能出現一次。

上圖是乙個部分填充的有效的數獨。

數獨部分空格內已填入了數字，空白格用'.'表示。

示例 1:

輸入:[

["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"]
]輸出:true

輸入:[

["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"]
]輸出:false解釋:除了第一行的第乙個數字從5改為8以外，空格內其他數字均與 示例1 相同。
但由於位於左上角的 3x3 宮內有兩個 8 存在, 因此這個數獨是無效的。

數獨有效必須滿足三個條件：

1. 每一行1-9

2. 每一列1-9

3. 每個3*3的方塊1-9

所以可以用三個字典來記錄行、列和方塊的已有元素情況。比如

row[1] = [1, 3, 5]就代表第一行已經出現了1， 3和5，如果下乙個3又出現在了第一行，就說明數獨無效。

class solution(object):

def isvalidsudoku(self, board):
""":type board: list[list[str]]
:rtype: bool
"""from collections import defaultdict
row, column, squre = defaultdict(set), defaultdict(set), defaultdict(set)
for i in range(9):
for j in range(9):
if board[i][j].isdigit(): #排除掉空的情況
if board[i][j] in row[i] or board[i][j] in column[j] or (board[i][j]) in squre[(i // 3, j // 3)]:
return false
else:
row[i].add(board[i][j])
column[j].add(board[i][j])
squre[(i // 3, j // 3)].add(board[i][j])
return true

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