leetcode 36题“Valid Sudoku”，描述如下

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.

这道题是数独问题，规则很简单每个九宫格每行每列不能有重复数字，比较笨的方法是分开遍历3次，每次分别解决行、列、九宫格的问题。比较好的解决方式只需要一次遍历如下：

/** * @param {character[][]} board * @return {boolean} */
var isValidSudoku = function(board) {
    var a = new Array(9),
        b = new Array(9),
        c = new Array(9);
    for (var k = 0; k < 9; k++) {
        a[k] = new Array(9);
        b[k] = new Array(9);
        c[k] = new Array(9);
    }

    for (var i = 0; i < 9; i++) {
        for (var j = 0; j < 9; j++) {
            var temp = board[i][j];
            if (temp === ".") {
                continue;
            }
            if (a[i][temp - 1] || b[temp - 1][j] || c[Math.floor(i / 3) * 3 + Math.floor(j / 3)][temp - 1]) {
                return false;
            }
            a[i][temp - 1] = b[temp - 1][j] = c[Math.floor(i / 3) * 3 + Math.floor(j / 3)][temp - 1] = true;
        }
    }
    return true;
};