36. Valid Sudoku

36. Valid Sudoku.swift

class Solution {
    func isValidSudoku(_ board: [[Character]]) -> Bool {
        var rowSet = [Set<Character>](repeating: Set<Character>(), count: 9)
        var colSet = [Set<Character>](repeating: Set<Character>(), count: 9)
        var squareSet = [Set<Character>](repeating: Set<Character>(), count: 9)

        for (rowIndex, row) in board.enumerated() {
            for (colIndex, character) in row.enumerated() {
                if character == Character(".") {
                    continue
                }
                guard !rowSet[rowIndex].contains(character) else { // 행별 값 포함여부
                    return false
                }
                rowSet[rowIndex].insert(character)
                guard !colSet[colIndex].contains(character) else { // 열별 값 포함여부
                    return false
                }
                colSet[colIndex].insert(character)
                
                let squareIndex = (rowIndex / 3) * 3 + (colIndex / 3)
                guard !squareSet[squareIndex].contains(character) else {
                    return false
                }
                squareSet[squareIndex].insert(character)
            }
        }
        return true
    }
}