36. Valid Sudoku

Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules :

1. Each row must contain the digits 1-9 without repetition.
2. Each column must contain the digits 1-9 without repetition.
3. Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition.

Note:

• A Sudoku board (partially filled) could be valid but is not necessarily solvable.
• Only the filled cells need to be validated according to the mentioned rules.

Example 1:

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

Example 2:

Input: board =
[["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"]]
Output: false
Explanation: Same as Example 1, except with the **5** in the top left corner being modified to **8**. Since there are two 8's in the top left 3x3 sub-box, it is invalid.

Constraints:

• board.length == 9
• board[i].length == 9
• board[i][j] is a digit or '.'.

# @lc code=start
using LeetCode

function is_valid_sudoku(board::Vector{Vector{Char}})::Bool
    function check_line(i::Int)::Bool
        s = replace(join(board[i]), "." => "")
        return length(s) == length(Set{Char}(s))
    end
    function check_col(i::Int)::Bool
        s = replace(join(board[k][i] for k in 1:9), '.' => "")
        return length(s) == length(Set{Char}(s))
    end
    function check_box(i::Int, j::Int)::Bool
        s = replace(join(board[i + p1][j + p2] for p1 in 1:3 for p2 in 1:3), "." => "")
        return length(s) == length(Set{Char}(s))
    end
    return all(check_line(i) && check_col(i) for i in 1:9) &&
           all(check_box(3 * (i - 1), 3 * (j - 1)) for i in 1:3 for j in 1:3)
end

# @lc code=end

is_valid_sudoku (generic function with 1 method)

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