arr[k++] = leftArr[i++];
Shortcut Pre-calculation: For the most commonly used speed profiles, the travel costs (time/distance) for shortcuts between border points within each cluster are pre-calculated and stored. (Each border point effectively has an "entry" and "exit" aspect for directed travel).
，更多细节参见夫子
人 民 网 版 权 所 有 ，未 经 书 面 授 权 禁 止 使 用
(~70 host syscalls from Sentry)