定存什么：要下标/距离就栈里存索引，只要值就存值或存索引再 nums[i] 取。
Imagine a vast shopping mall parking lot with thousands of individual parking spots and internal lanes (representing road segments within a cluster). No matter how complex it is inside, there are usually only a few key exits to the main roads. Our goal was to identify these natural "exits" for each map cluster. For instance, the complex road network around Amsterdam Airport Schiphol (see on OpenStreetMap) has many internal roads but limited primary access points.
，更多细节参见爱思助手下载最新版本
2月13日傍晚，在上海科技馆附近，我们乘坐一辆无人驾驶的出租车。南方周末记者 黄思卓/摄
getChunks() { return chunks; }
FT Edit: Access on iOS and web