class Solution:
    '''
    Time Complexity: O(n log(n))
    Space Complexity: O(n)
    where, n is the number of cars.
    '''
    def carFleet(self, target: int, position: List[int], speed: List[int]) -> int:
        cars = [(position[i], speed[i]) for i in range(len(position))]
        cars.sort(key=lambda x: x[0])
        time = [(target - distance)/velocity for distance, velocity in cars]
        fleets = []
        for t in time:
            while fleets and t >= fleets[-1]:
                fleets.pop()
            fleets.append(t)
        return len(fleets)