Car pooling [var. of Meeting rooms II]

Time: O(NLogN); Space: O(N); medium

You are driving a vehicle that has capacity empty seats initially available for passengers.

The vehicle only drives east (ie. it cannot turn around and drive west.)

Given a list of trips, trip[i] = [num_passengers, start_location, end_location] contains information about the i-th trip: * the number of passengers that must be picked up, and * the locations to pick them up and drop them off.

The locations are given as the number of kilometers due east from your vehicle’s initial location.

Return true if and only if it is possible to pick up and drop off all passengers for all the given trips.

Example 1:

Input: trips = [[2,1,5],[3,3,7]], capacity = 4

Output: False

Example 2:

Input: trips = [[2,1,5],[3,3,7]], capacity = 5

Output: True

Example 3:

Input: trips = [[2,1,5],[3,5,7]], capacity = 3

Output: True

Example 4:

Input: trips = [[3,2,7],[3,7,9],[8,3,9]], capacity = 11

Output: True

Constraints:

  • len(trips) <= 1000

  • len(trips[i]) == 3

  • 1 <= trips[i][0] <= 100

  • 0 <= trips[i][1] < trips[i][2] <= 1000

  • 1 <= capacity <= 100000

Hints:

  1. Sort the pickup and dropoff events by location, then process them in order.

[1]:

class Solution1(object):
    """
    Time:  O(NLogN)
    Space: O(N)
    """
    def carPooling(self, trips, capacity):
        """
        :type trips: List[List[int]]
        :type capacity: int
        :rtype: bool
        """
        line = [x for num, start, end in trips for x in [[start, num], [end, -num]]]
        line.sort()

        for _, num in line:
            capacity -= num
            if capacity < 0:
                return False
        return True

[2]:

s = Solution1()
trips = [[2,1,5],[3,3,7]]
capacity = 4
assert s.carPooling(trips, capacity) == False

trips = [[2,1,5],[3,3,7]]
capacity = 5
assert s.carPooling(trips, capacity) == True

trips = [[2,1,5],[3,5,7]]
capacity = 3
assert s.carPooling(trips, capacity) == True

trips = [[3,2,7],[3,7,9],[8,3,9]]
capacity = 11
assert s.carPooling(trips, capacity) == True