思路：① 算每辆车到达时间 = (target - position) / speed；② 按位置降序排序；③ 单调递增栈：仅当当前时间 栈顶时间时压栈（新车队），否则合并。栈长即为车队数。可优化为用变量代替栈。
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She sips tea throughout the interview in an effort to protect her voice, which is "really delicate" - not from the concerts, but because "I've been talking too much to my friends".
One challenge is having enough training data. Another is that the training data needs to be free of contamination. For a model trained up till 1900, there needs to be no information from after 1900 that leaks into the data. Some metadata might have that kind of leakage. While it’s not possible to have zero leakage - there’s a shadow of the future on past data because what we store is a function of what we care about - it’s possible to have a very low level of leakage, sufficient for this to be interesting.