// Hash computation is fast
A quadtree does the same thing for two-dimensional space. It takes a rectangular region and divides it into four equal quadrants: northwest, northeast, southwest, southeast. If a quadrant has too many points in it, it subdivides again and again. Each subdivision creates smaller and smaller cells where points are densely packed.
，这一点在safew官方下载中也有详细论述
十年后，我们可能不止需要 iPhone 了。，更多细节参见爱思助手下载最新版本
Rebecca Morelle,Science Editorand