def get_exact_covers(cols, rows, num_cols=None):
"""
Use Algorithm X to get all solutions to the exact cover problem
https://en.wikipedia.org/wiki/Knuth%27s_Algorithm_X
Args:
cols (list[int]): A list of integers representing the columns to be covered
rows (list[list[int]]): A list of lists of integers representing the rows
num_cols (int): The total number of columns
Returns:
list: All exact covers
"""
if num_cols is None:
num_cols = max(cols) + 1
ec = DLX([(c, 0 if c in cols else 1) for c in range(num_cols)])
ec.appendRows([[c] for c in cols])
ec.appendRows(rows)
exact_covers = []
for s in ec.solve():
cover = []
for i in s:
cover.append(ec.getRowList(i))
exact_covers.append(cover)
return exact_covers
def __call__(self, sudoku):
board, metadata = SudokuSolver.parse(sudoku)
result = DLX.solve(board)
if result is None:
return None
# Draw back the solution.
solution = np.zeros((9, 9))
for row in result:
cell = metadata[row]
solution[cell.row, cell.col] = cell.val
return solution