d = {"1": None}
https://feedx.site
，这一点在91视频中也有详细论述
It meant not all councils needed to make changes to meet the new rules, but the BBC approached each local authority responsible for waste collection to find out what was happening in their area. Further councils have provided responses since this article was first published.
The quadtree is the two-dimensional case of a broader family of space-partitioning data structures. Octrees extend the same idea to three dimensions (splitting cubes into eight children), KD-trees use alternating axis-aligned splits (splitting along x, then y, then x again), and R-trees group nearby objects into bounding rectangles. Each variant makes different tradeoffs between construction time, query speed, and update cost.
* @param arr 待排序数组