squirrel/36. Valid Sudoku.py at master · hualazimi0425/squirrel · GitHub

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import collections
from typing import List


def isValidSudoku(board: List[List[str]]) -> bool:
    # init hash map
    rows = [{} for i in range(9)]
    columns = [{} for j in range(9)]
    boxes = [{} for i in range(9)]
    # valid board
    for i in range(9):
        for j in range(9):
            num = board[i][j]
            if num != '.':
                num = int(num)
                box_index = (i // 3) * 3 + j // 3
                # keep the current cell value
                rows[i][num] = rows[i].get(num, 0) + 1
                columns[j][num] = columns[j].get(num,0) + 1
                boxes[box_index][num] = boxes[box_index].get(num,0) + 1
                # check if this value has been already seen before
                if rows[i][num] > 1 or columns[j][num] > 1 or boxes[box_index][num] > 1:
                    return False
    return True

print(isValidSudoku([
  ["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"]
]))

print(isValidSudoku([
  ["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"]
]))

a = collections.defaulftdict(int)