Car Pooling

ID: 1094

There is a car with capacity empty seats. The vehicle only drives east (i.e., it cannot turn around and drive west).

You are given the integer capacity and an array trips where trip[i] = [numPassengersi, fromi, toi] indicates that the ith trip has numPassengersi passengers and the locations to pick them up and drop them off are fromi and toi respectively. The locations are given as the number of kilometers due east from the car's initial location.

Return true if it is possible to pick up and drop off all passengers for all the given trips, or false otherwise.

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

Idea

PriorityQueue / Array storage

Approach 1: Construct PriorityQueue for [startStop, endStop] and pop one by one to check if there's a stop that result in a load > capacity

Approach 2: Construct a simple array of length 1001, since there's maximum of 1000 stops. Check each trip can add corresponding passenger number to start stop and minus number to end stop

Iterate through all stops and sum all, if there's a point that the load > capacity, return false

Code

public boolean carPooling(int[][] trips, int capacity) {
    int[] stops = new int[1001];
    int load = 0;
    for(int i = 0; i<trips.length; i++){
        stops[trips[i][1]]+=trips[i][0];
        stops[trips[i][2]]-=trips[i][0];
    }
    
    for(int i = 0; i<stops.length; i++){
        load+=stops[i];
        if(load>capacity){
            return false;
        }
    }
    return true;
}