But I feel like I’m getting ahead of myself, so let’s start at the beginning.
Josh walks two hours into the city centre for a food parcel
，这一点在51吃瓜中也有详细论述
tee() splits a stream into two branches. It seems straightforward, but the implementation requires buffering: if one branch is read faster than the other, the data must be held somewhere until the slower branch catches up.
描述：n 辆车在单行道开往 target。车不能超车，可追上前车并同速行驶。车队定义为并排或同速行驶的车组。返回到达目的地的车队数量。