arrivalTime[i] = (dist[i] - 1) / speed[i] + 1;
向上取整, 等同于(dist[i] + speed[i] - 1) / speed[i]
如: (6+3-1)/3=2, 与6/3=2相同, 而(5+3-1)/3=2, 会比5/3=1多1, 达到了向上取整的目的
arrivalTime[i] = (dist[i] - 1) / speed[i] + 1;
向上取整, 等同于(dist[i] + speed[i] - 1) / speed[i]
如: (6+3-1)/3=2, 与6/3=2相同, 而(5+3-1)/3=2, 会比5/3=1多1, 达到了向上取整的目的