来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/valid-sudoku
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题目

判断一个 9x9 的数独是否有效。只需要根据以下规则，验证已经填入的数字是否有效即可。

数字 1-9 在每一行只能出现一次。
数字 1-9 在每一列只能出现一次。
数字 1-9 在每一个以粗实线分隔的 3x3 宫内只能出现一次。

image.png

上图是一个部分填充的有效的数独。

数独部分空格内已填入了数字，空白格用 '.' 表示。

示例 1:

输入:
[
  ["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"]
]
输出: true

示例 2:

输入:

[
  ["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"]
]
输出: false
解释: 除了第一行的第一个数字从 5 改为 8 以外，空格内其他数字均与 示例1 相同。
     但由于位于左上角的 3x3 宫内有两个 8 存在, 因此这个数独是无效的。

说明:

一个有效的数独（部分已被填充）不一定是可解的。
只需要根据以上规则，验证已经填入的数字是否有效即可。
给定数独序列只包含数字 1-9 和字符 '.' 。
给定数独永远是 9x9 形式的。

方法1:查找横的、竖的、九宫格是否有重复

   func isValidSudoku(_ board: [[Character]]) -> Bool {
        
        for i in 0..<board.count {
            
            let array = board[i]
            if !isValidRow(board, i) {
                return false
            }
            if !isValidLine(board, i) {
                return false
            }
            
            if i % 3 == 0 {
                for j in 0..<array.count {
                   
                    if j % 3 == 0 {
                        if !isValidSquare(board, i, j) {
                            return false
                        }
                    }
                }
            }
            
        }
        return true
    }
    func isValidRow(_ board: [[Character]], _ row: Int) -> Bool {
        //判断行row
        let currentRowLine = board[row]
        var boardDic = [Character: Int]()
        
        for character in currentRowLine {
            
            if character == "." {
                continue
            }
            if boardDic[character] == 1 {
                
                return false
            }
            boardDic[character] = 1
        }
        return true
    }
    func isValidLine(_ board: [[Character]], _ line: Int) -> Bool {
        //判断列line
        var boardDic = [Character: Int]()
        for characterArr in board {
            
            if characterArr[line] == "." {
                continue
            }
            if boardDic[characterArr[line]] == 1 {
                
                return false
            }
            boardDic[characterArr[line]] = 1
        }
        return true
    }
    func isValidSquare(_ board: [[Character]], _ row: Int, _ line: Int) -> Bool {
        
        var boardDic = [Character: Int]()
        
        //判断此九宫格
        boardDic = [Character: Int]()
        
        for i in row...row+2 {
            
            for j in line...line+2 {
                
                if board[i][j] == "." {
                    continue
                }
                if boardDic[board[i][j]] == 1 {
                    
                    return false
                }
                boardDic[board[i][j]] = 1
            }
        }
        
        return true
    }