tvl-depot/users/wpcarro/scratch/facebook/n-queens.py

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def print_board(board):
result = []
for row in range(8):
r = []
for col in range(8):
r.append("X" if col == board[row] else "-")
result.append(" ".join(r))
print("\n".join(result))
print()
def can_place(board, row, col):
column_occupied = not any([board[i] == col for i in range(row)])
diagonals_clear = True
for r in range(row):
w = abs(col - board[r])
h = abs(r - row)
if w == h:
diagonals_clear = False
break
return all([column_occupied, diagonals_clear])
def init_board():
board = []
for row in range(8):
board.append(None)
return board
def copy_board(board):
return board[:]
def n_queens():
do_n_queens(init_board(), 0, 0)
def do_n_queens(board, row, col):
if row == 8:
print_board(board)
return
for i in range(col, 8):
if can_place(board, row, i):
copy = copy_board(board)
copy[row] = i
do_n_queens(copy, row + 1, 0)
n_queens()