36.valid-sudoku.py

#
# @lc app=leetcode id=36 lang=python3
#
# [36] Valid Sudoku
#

# @lc code=start
import collections


class Solution:
    def isValidSudoku(self, board: List[List[str]]) -> bool:
        rows=collections.defaultdict(set)
        cols=collections.defaultdict(set)
        squares=collections.defaultdict(set)
        for i in range(9):
            for j in range(9):
                if board[i][j]==".":
                    continue
                if board[i][j] in rows[i]:
                    return False
                if board[i][j] in cols[j]:
                    return False
                if board[i][j] in squares[(i//3,j//3)]:
                    return False
                rows[i].add(board[i][j])
                cols[j].add(board[i][j])
                squares[(i//3,j//3)].add(board[i][j])
        return True
        
# @lc code=end