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.
不过完美日记的“哑火”并非一朝一夕，而是有一条清晰可查的下行曲线。
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线买到手，不够长或者太长，都得自己想办法，要么挪电视，要么挪家具。
Екатерина Щербакова (ночной линейный редактор)