def annotate(minefield):

if(minefield == []):

return []

verify_board(minefield)

row_len = len(minefield[0])

col_len = len(minefield)

board = [list(row) for row in minefield]

for index1 in range(col_len):

for index2 in range(row_len):

if board[index1][index2] != ' ':

continue

low = max(index2 - 1, 0)

high = min(index2 + 2, row_len + 2)

counts = minefield[index1][low:high].count('*')

if(index1 > 0):

counts += minefield[index1 - 1][low:high].count('*')

if(index1 < col_len - 1):

counts += minefield[index1 + 1][low:high].count('*')

if counts == 0:

continue

board[index1][index2] = str(counts)

return ["".join(row) for row in board]

def verify_board(minefield):

# Rows with different lengths

row_len = len(minefield[0])

if not all(len(row) == row_len for row in minefield):

raise ValueError("Invalid board")

# Unknown character in board

character_set = set()

for row in minefield:

character_set.update(row)

if character_set - set(' *'):

raise ValueError("Invalid board")