August 2017
Intermediate to advanced
360 pages
8h 35m
Chinese
Content preview from 算法技术手册（原书第2 版）
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空间树结构
｜
289
空间树结构
图 10-14：使用四叉树的碰撞检测
10.7.1 输入 / 输出
输入是一棵四叉树，它由平面上的一个二维点集
P
构建而成。
为了获得最佳性能，范围查询会返回四叉树中的
结点
，这样可以在目标矩形完全覆盖子
树中点时直接返回。碰撞检测的结果是目标点与已有点的交集。
10.7.2 解决方案
在例
10-4
中，
QuadTree
和
QuadNode
结构
展示了基本的四叉树
Python
实现，
smaller2k
和
larger2k
辅助方法确保初始区域的边长为
2
的幂次，
Region
类表示一块矩形区域。
例
10-4
：四叉树的
QuadNode
实现
class Region:
def __init__(self, xmin,ymin, xmax,ymax):
"""
从两点
(xmin, ymin)
和
(xmax, ymax)
出发创建区域。
如果这两个点不是区域的左下角和右上角坐标，相应地进行调整。
"""
self.x_min = xmin if xmin < xmax else xmax
self.y_min = ymin if ymin < ymax else ymax
self.x_max = xmax if xmax > xmin else xmin
self.y_max = ymax if ymax > ymin else ymin
class QuadNode:
def __init__(self, region, pt = ...
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