def solveSudoku(self, board: List[List[str]]) -> None:

"""

row = [[False for _ in range(9)] for _ in range(9)]

column = [[False for _ in range(9)] for _ in range(9)]

box = [[False for _ in range(9)] for _ in range(9)]

to_fill = [[board[i][j] == "." for j in range(9)] for i in range(9)]

missed = 0

for i in range(9):

for j in range(9):

if board[i][j] != ".":

k = i // 3 * 3 + j // 3

n = ord(board[i][j]) - 49

row[i][n] = True

column[j][n] = True

box[k][n] = True

else:

missed += 1

def can_fill(i, j, v):

return not row[i][v] and not column[j][v] and not box[i // 3 * 3 + j // 3][v]

def dfs(i, j, cnt):

if cnt == 0:

# all done

return 0

if to_fill[i][j]:

for l in range(0, 9):

if can_fill(i, j, l):

board[i][j] = chr(l + 49)

row[i][l] = True

column[j][l] = True

box[i // 3 * 3 + j // 3][l] = True

if (dfs(i + 1, 0, cnt - 1) if j == 8 else dfs(i, j + 1, cnt - 1)) == 0:

# all done

return 0

row[i][l] = False

column[j][l] = False

box[i // 3 * 3 + j // 3][l] = False

board[i][j] = "."

# no resolution

return -1

else:

if j == 8:

return dfs(i + 1, 0, cnt)

else:

return dfs(i, j + 1, cnt)