1094. Car Pooling (M)

Car Pooling (M)

题目

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:

1. trips.length <= 1000
2. trips[i].length == 3
3. 1 <= trips[i][0] <= 100
4. 0 <= trips[i][1] < trips[i][2] <= 1000
5. 1 <= capacity <= 100000

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题意

一辆有容量限制的公交车一路向东，在每个里程点会有若干乘客上车或下车，问能否运输所有乘客。

思路

求出每个里程点的人员变动数量，在经过这些历程点时车上人数进行相应变化，如果某一点车上人数超出限制，说明无法运输所有乘客。

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代码实现

Java

class Solution {
    public boolean carPooling(int[][] trips, int capacity) {
        int[] change = new int[1001];
        for (int[] trip : trips) {
            change[trip[1]] += trip[0];
            change[trip[2]] -= trip[0];
        }
        int remain = 0;
        for (int value : change) {
            remain += value;
            if (remain > capacity) {
                return false;
            }
        }
        return true;
    }
}