36. 有效的数独

题目链接：https://leetcode-cn.com/problems/valid-sudoku/submissions/

参考高票题解讲解，很棒。3*3矩阵的序号通过计算存储,恰好能类似运用在73题。
swift版代码

执行用时：80 ms, 在所有 Swift 提交中击败了100.00%的用户
内存消耗：13.9 MB, 在所有 Swift 提交中击败了76.58%的用户

class Solution {
    func isValidSudoku(_ board: [[Character]]) -> Bool {
        var row = [[Int]].init(repeating:
        [Int].init(repeating: 0, count: 10), count: 9)
        var col = [[Int]].init(repeating:
        [Int].init(repeating: 0, count: 10), count: 9)
        var block = [[Int]].init(repeating:
        [Int].init(repeating: 0, count: 10), count: 9)
        for i in 0 ..< 9 {
            for j in 0 ..< 9 {
                if board[i][j] == "." {
                    continue
                }
                let num = Int(String(board[i][j]))!
                if row[i][num] == 1 {
                    return false
                }
                if col[j][num] == 1 {
                    return false
                }
                if block[(i/3)*3 + (j/3)][num] == 1 {
                    return false
                }
                row[i][num] = 1
                col[j][num] = 1
                block[(i/3)*3 + (j/3)][num] = 1
            }
        }
        return true
    }
}