LeetCode36 有效的數獨

2021-09-12 05:44:35 字數 1919 閱讀 3208

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

示例 2:

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。

說明:

乙個有效的數獨(部分已被填充)不一定是可解的。

只需要根據以上規則,驗證已經填入的數字是否有效即可。

給定數獨序列只包含數字 1-9 和字元 『.』 。

給定數獨永遠是 9x9 形式的。

暫時沒有想出好的演算法,先試試暴力解法:

演算法流程:

(1)遍歷每一行,看看是否有重複的數

(2)遍歷每一列,看看是否有重複的數

(3)遍歷每乙個小的3*3宮,看看是否有重複的數

實際上,可以使用空間換時間,在遍歷每一行的時候,就把這些資料都儲存下來,使用集合來篩去重複的數字,這樣即可實現判重

c++**:

class solution 

else if (i < 6)

else

} // 開始進行逐行判重

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

}} return true;

}};

執行效率:

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