[코드코드] 수도쿠-Blue

```python
def sudoku():
board = [
[5, 3, 0, 0, 7, 0, 0, 0, 0],
[6, 0, 0, 1, 9, 5, 0, 0, 0],
[0, 9, 8, 0, 0, 0, 0, 6, 0],
[8, 0, 0, 0, 6, 0, 0, 0, 3],
[4, 0, 0, 8, 0, 3, 0, 0, 1],
[7, 0, 0, 0, 2, 0, 0, 0, 6],
[0, 6, 0, 0, 0, 0, 2, 8, 0],
[0, 0, 0, 4, 1, 9, 0, 0, 5],
[0, 0, 0, 0, 8, 0, 0, 7, 9]
]

solve(board)
print_board(board)

def solve(board):
find = find_empty(board)
if not find:
return True
else:
row, col = find

for num in range(1, 10):
if is_valid(board, num, (row, col)):
board[row][col] = num

if solve(board):
return True

board[row][col] = 0

return False

def is_valid(board, num, pos):
for i in range(len(board[0])):
if board[pos[0]][i] == num and pos[1] != i:
return False

for i in range(len(board)):
if board[i][pos[1]] == num and pos[0] != i:
return False

box_x = pos[1] // 3
box_y = pos[0] // 3

for i in range(box_y*3, box_y*3 + 3):
for j in range(box_x * 3, box_x*3 + 3):
if board[i][j] == num and (i,j) != pos:
return False

return True

def print_board(board):
for i in range(len(board)):
if i % 3 == 0 and i != 0:
print(\