※ 引述《Rushia (みけねこ的鼻屎)》之銘言：
: 36. Valid Sudoku
: 給你一個二維字元陣列表示一個數獨，包含1~9和表示空白的.字元，一個合法數獨
: 滿足以下條件：
: 1.每行和每列最多出現一種數字一次
: 2.一個3x3九宮格內只會出現一種數字一次
: 3.數獨可能無解（無法填滿數字），但是只有滿足1或2才是Invalid
: 判斷給定的棋盤是否是一個合法數獨
: Example：
: https://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/Sudoku-by-L2G-20050714.svg/250px-Sudoku-by-L2G-20050714.svg.png
: Input: board =
: [["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"]]
: Output: true
可惡 就我用最基礎的方法
思路就一樣是用set檢查每行和每列是否有重複 再檢查每個 3 * 3 區塊是否有重複
幸好九宮格的大小都固定所以套四層迴圈也沒關係