将列表附加到皇后区难题的每个唯一解决方案。我不知道为什么最后一个解决方案是附加到列表中的唯一解决方案？

Question

我正在尝试将 N 皇后拼图的每个单独解决方案保存到列表中。但是，当我尝试将每个列表添加为子列表时，只有最后一个解决方案被添加到列表中（10 次），而不是 10 个单独的解决方案。我的目标是确保每次我运行只打印尚未找到的新解决方案并将其添加到列表中。

def share_diagonal(x0, y0, x1, y1):
    """ Is (x0, y) on the same shared diagonal with (x1, y1)? """
    dx = abs(x1 - x0)  # Calc the absolute y distance
    dy = abs(y1 - y0)  # Calc the absolute x distance
    return dx == dy  # They clash if dx == yx


def col_clashes(bs, c):
    """ Return True if the queen at column c clashes
        with any queen to its left.
    """
    for i in range(c):  # Look at all columns to the left of c
        if share_diagonal(i, bs[i], c, bs[c]):
            return True
    return False  # No clashes - col c has a safe placement


def has_clashes(the_board):
    """ Determine whether we have any queens clashing on the diagonal.
        We're assuming here that the_board is a permutation of column
        numbers, so we're not explicitly checking row or column clashes.
    """
    for col in range(1, len(the_board)):
        if col_clashes(the_board, col):
            return True
    return False

solutions = []

def main(board_size):
    import random
    global solutions
    rng = random.Random()  # Instantiate a generator

    bd = list(range(board_size))  # Generate the initial permutation
    num_found = 0
    tries = 0
    while num_found < 10:
        rng.shuffle(bd)
        tries += 1
        if not has_clashes(bd):
            print("Found solution {0} in {1} tries.".format(bd, tries))
            solutions.append(bd)  # This is the section in which I am trying to save each individual solution into a list. 
            tries = 0
            num_found += 1


main(8)
for i in solutions:
    print(i)  # When I print off the list, all items in the list are replica's of the last solution found. Not each individual solution. I don't know why this is occurring.

Answer 1

只是改变

solutions.append(bd)

到

solutions.append(list(bd))

创建当前解决方案的副本。在列表中出现相同解决方案 10 次的问题是因为您在结果列表中添加了对 bd 的引用，但随后就地随机播放了列表 bd。

为了跳过重复的解决方案更改

if not has_clashes(bd):

到

if not has_clashes(bd) and bd not in solutions:

将列表附加到皇后区难题的每个唯一解决方案。我不知道为什么最后一个解决方案是附加到列表中的唯一解决方案？

Appending the list with each unique solution to the Queens Puzzle. I don't know why the last solution is the only solution appended to the list?

python

n-queens