LeetCode #36 Valid Sudoku

LeetCode #36 Valid Sudoku

Question

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.

The Sudoku board could be partially filled, where empty cells are filled with the character '.'.

A partially filled sudoku which is valid.

Note:
A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.

Solution

Approach #1

class Solution {
    func isValidSudoku(_ board: [[Character]]) -> Bool {
        for i in 0..<9 {
            var rowCharSet = Set<Character>()
            var colCharSet = Set<Character>()
            var cellCharSet = Set<Character>()
            let point: Character = "."
            for j in 0..<9 {
                if board[i][j] != point {
                    if rowCharSet.contains(board[i][j]) { return false }
                    rowCharSet.insert(board[i][j])
                }
                if board[j][i] != "." {
                    if colCharSet.contains(board[j][i]) { return false }
                    colCharSet.insert(board[j][i])
                }
                let p = i / 3 * 3 + j / 3
                let q = i % 3 * 3 + j % 3
                if board[p][q] != "." {
                    if cellCharSet.contains(board[p][q]) { return false }
                    cellCharSet.insert(board[p][q])
                }
            }
        }
        return true
    }
}

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