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.
今年春节假期，中国游、中国购持续火热，越来越多外国游客来到中国，沉浸式体验丰富年俗和传统文化。从提升入境服务便利性，到发布多语种春节民俗地图，再到完善支付环境……有关部门和企业推出一系列举措，让外国游客方便来、欢快玩、舒心购。
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However, this flexibility came at a cost for complex routes:
Because every interaction passes through runEffect, we can easily implement a redaction layer to scrub personally identifiable information, like credit card numbers or emails, before they ever hit the trace log.