课程调度问题：LeetCode 630. Course Schedule III

题目描述：
There are n different online courses numbered from 1 to n. Each course has some duration(course length) t and closed on dth day. A course should be taken continuously for t days and must be finished before or on the dth day. You will start at the 1st day.

Given n online courses represented by pairs (t,d), your task is to find the maximal number of courses that can be taken.
示例：
Input: [[100, 200], [200, 1300], [1000, 1250], [2000, 3200]]
Output: 3

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解题思路：

1. 将课程按due time排序，due time排序在前的表示优先级较高，需要先完成；
2. 遍历排序后的课程，若某个课程可在due time前结束，则将该课程的耗费时间加入调度list中，并更新已花费的时间consumingTIme的值；
3. 若某个课程不可在due time前结束，则首先判断该课程耗费时间是否比list中最长的耗费时间还要长，若是，则不添加该课程；若不是，则删除list中最长的耗费时间并将该时间加入list中。

原理：

• 按due time排序可保证所有课程较好的时间顺序加入li