leetcode 每日一题 36. 有效的数独

一次遍历

思路:

对二维数组每个元素进行遍历，遍历的同时记录下当前元素在行、列和3x3格中出现的次数，如果大于1返回False，遍历结束则返回True。

代码：

class Solution:
    def isValidSudoku(self, board: List[List[str]]) -> bool:
        rows = [{} for i in range(9)]
        columns = [{} for i in range(9)]
        boxes = [{} for i in range(9)]
        for i in range(9):
            for j in range(9):
                if board[i][j] != '.':
                    num = int(board[i][j])
                    boxIndex = (i//3)*3 + j//3
                    rows[i][num] = rows[i].get(num,0)+1
                    columns[j][num] = columns[j].get(num,0)+1
                    boxes[boxIndex][num] = boxes[boxIndex].get(num,0)+1
                    if rows[i][num]>1 or columns[j][num] >1 or boxes[boxIndex][num]>1:
                        return False
        return True