类似整理扑克牌：每次拿一张新牌，插入到已排好序的牌堆中合适位置
union object_info *h = free_list[classno];
，详情可参考夫子
The spatial view (the grid of rectangles) and the tree view (the hierarchy of nodes) represent the same structure. Searching for a point means walking down the tree: at each node, you check which of the four children contains your target coordinate and recurse into that child. You never visit the other three.，详情可参考91视频
The recent surge of more than 2,000 immigration officers to the state inspired nationwide protests after two US citizens were killed by federal agents last month.。搜狗输入法2026对此有专业解读