# #StackBounty: #python #algorithm #python-2.7 #sudoku Sudoku solver recursive solution

### Bounty: 50

Here is my code in Python 2.7 for a Sudoku resolver. Any advice on performance improvement, code bugs or general code style advice is appreciated.

My major idea is:

1. Using method generate some random data, then using `check_invalid` to see if it is a valid Sudoku
2. If from 1, it is a valid Sudoku, then I will call `resolve_sudoku` to fill valid values

I find my code sometimes run a long time without completion. Are there any code bugs you can find?

``````import random
from collections import defaultdict
found = False
def check_invalid(matrix):
# check for each row
for row in range(len(matrix)):
cur_row = set()
for col in range(len(matrix[0])):
if matrix[row][col] == 0:
continue
elif 1 <= matrix[row][col] <= 9:
if matrix[row][col] in cur_row:
return False
else:
else:
return False # invalid number
# check each col
for col in range(len(matrix[0])):
cur_col = set()
for row in range(len(matrix)):
if matrix[row][col] == 0:
continue
elif 1 <= matrix[row][col] <= 9:
if matrix[row][col] in cur_col:
return False
else:
else:
return False # invalid number
# check each 3*3 square
for start_row in [0,3,6]:
for start_col in [0,3,6]:
cur_square = set()
for row in range(start_row, start_row+3):
for col in range(start_col, start_col + 3):
if matrix[row][col] == 0:
continue
elif 1 <= matrix[row][col] <= 9:
if matrix[row][col] not in cur_square:
else:
return False
else:
return False # invalid value
return True

def resolve_sudoku(matrix, row_map, col_map, square_map, cur_row, cur_col):
global found
if found:
return
if cur_row == len(matrix):
found = True
for r in matrix:
print r
elif cur_col == len(matrix[0]):
resolve_sudoku(matrix, row_map, col_map, square_map, cur_row+1, 0)
elif matrix[cur_row][cur_col] != 0:
resolve_sudoku(matrix, row_map, col_map, square_map, cur_row, cur_col+1)
else:
for val in range(1,10):
square_x = cur_row / 3
square_y = cur_col / 3
if val in row_map[cur_row] or val in col_map[cur_col] or val in square_map[(square_x, square_y)]:
continue
else:
matrix[cur_row][cur_col] = val
resolve_sudoku(matrix, row_map, col_map, square_map, cur_row, cur_col+1)
row_map[cur_row].remove(val)
col_map[cur_col].remove(val)
square_map[(square_x, square_y)].remove(val)
matrix[cur_row][cur_col] = 0
if found:
return
if __name__ == "__main__":
matrix = []
for row in range(9):
cur_row = []
for col in range(9):
if random.random() < 0.1:
cur_row.append(random.randint(1,9))
else:
cur_row.append(0)
matrix.append(cur_row)
for r in matrix:
print r
re = check_invalid(matrix)
print re
if re:
# init for row map and col map
row_map = defaultdict(set)
col_map = defaultdict(set)
square_map = defaultdict(set)
for row in range(len(matrix)):
for col in range(len(matrix[0])):
square_x = row / 3
square_y = row / 3
if matrix[row][col] != 0: