八数码问题python代码深度优先

好的，以下是八数码问题的深度优先搜索的Python代码：

def dfs(start, target):
    stack = [(start, "")]
    visited = set()
    while stack:
        node, path = stack.pop()
        if node == target:
            return path
        if node in visited:
            continue
        visited.add(node)
        for move, delta in moves.items():
            next_node = apply_move(node, delta)
            if next_node is not None:
                stack.append((next_node, path + move))
    return None

def apply_move(node, delta):
    x, y = node.index("0") // 3, node.index("0") % 3
    dx, dy = delta
    nx, ny = x + dx, y + dy
    if 0 <= nx < 3 and 0 <= ny < 3:
        i, j = nx * 3 + ny, x * 3 + y
        return node[:j] + node[i] + node[j+1:i] + "0" + node[i+1:]
    else:
        return None

moves = {
    "U": (-1, 0),
    "D": (1, 0),
    "L": (0, -1),
    "R": (0, 1)
}

start = "123456780"
target = "087654321"
path = dfs(start, target)
print(path)

其中，`dfs` 函数实现了深度优先搜索，`apply_move` 函数实现了移动操作，`moves` 字典定义了四个方向的移动，`start` 和 `target` 分别是起始状态和目标状态。