可以写一个四叉树代码吗

当然可以，下面是一个简单的四叉树实现代码：

class QuadTree:
    def __init__(self, x1, y1, x2, y2, capacity=4):
        self.x1 = x1
        self.y1 = y1
        self.x2 = x2
        self.y2 = y2
        self.capacity = capacity
        self.points = []
        self.northwest = None
        self.northeast = None
        self.southwest = None
        self.southeast = None

    def insert(self, point):
        if len(self.points) < self.capacity:
            self.points.append(point)
        else:
            if self.northwest is None:
                self.subdivide()

            if self.northwest.contains(point):
                self.northwest.insert(point)
            elif self.northeast.contains(point):
                self.northeast.insert(point)
            elif self.southwest.contains(point):
                self.southwest.insert(point)
            else:
                self.southeast.insert(point)

    def subdivide(self):
        x_mid = (self.x1 + self.x2) / 2
        y_mid = (self.y1 + self.y2) / 2
        self.northwest = QuadTree(self.x1, self.y1, x_mid, y_mid, self.capacity)
        self.northeast = QuadTree(x_mid, self.y1, self.x2, y_mid, self.capacity)
        self.southwest = QuadTree(self.x1, y_mid, x_mid, self.y2, self.capacity)
        self.southeast = QuadTree(x_mid, y_mid, self.x2, self.y2, self.capacity)

    def contains(self, point):
        return self.x1 <= point[0] <= self.x2 and self.y1 <= point[1] <= self.y2

    def query(self, range):
        points_within_range = []
        if not self.intersects(range):
            return points_within_range

        for point in self.points:
            if range.contains(point):
                points_within_range.append(point)

        if self.northwest is None:
            return points_within_range

        points_within_range.extend(self.northwest.query(range))
        points_within_range.extend(self.northeast.query(range))
        points_within_range.extend(self.southwest.query(range))
        points_within_range.extend(self.southeast.query(range))

        return points_within_range

    def intersects(self, range):
        return not (self.x1 > range.x2 or self.x2 < range.x1 or self.y1 > range.y2 or self.y2 < range.y1)

这个四叉树类有以下方法：

- `__init__(self, x1, y1, x2, y2, capacity=4)`：初始化一个四叉树，x1, y1, x2, y2 是四叉树的边界，capacity 是每个节点最多容纳的点的数量。
- `insert(self, point)`：将一个点插入四叉树中。
- `subdivide(self)`：将节点分成四个子节点。
- `contains(self, point)`：判断一个点是否在当前节点内。
- `query(self, range)`：查询一个范围内的所有点，range 是一个矩形，表示要查询的范围。
- `intersects(self, range)`：判断一个范围是否与当前节点相交。