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。

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。

代码

/**
 * @param {character[][]} board
 * @return {boolean}
 */
var isValidSudoku = function(board) {
    let rows = {};
    let ranks = {};
    let react = {};
    let result = true;
    for(let n=0;n<board.length;n++){
        for(let m=0;m<board[n].length;m++){
            let value = board[n][m]
            if(value != '.'){
                
                if(!rows[n]){
                    rows[n] ={}
                }
                if(!ranks[m]){
                    ranks[m]={}
                }
           
                //条件一
                if(!rows[n][value]){
                    rows[n][value] = true
                }else{
                    result = false;
                }
                //条件二
                if(!ranks[m][value]){
                    ranks[m][value] = true;
                }else{
                    result = false;
                }
                //条件三
                
                let rowsN = Math.ceil((n+1)/3);
                let ranksM = Math.ceil((m+1)/3);
               
                if(!react[rowsN]){
                    react[rowsN] = {}
                }
                if( !react[rowsN][ranksM] ){
                    react[rowsN][ranksM] = {}
                }
                if(!react[rowsN][ranksM][value]){
                    react[rowsN][ranksM][value] = true
                }else{
                    result = false;
                }
            }
            
        }
    }

    return result
    
    
};