Input: MaxWorkLoad: example 10
       Timeslot and workload: example [(2, 6, 3), (3, 8, 2), ... ]
       The (2, 6, 3) is begin time, end time, and workload
       You can treat the 2, 6 as the UNIX epoch time.
       The time may not be integers, so instead of 2, it can be 2.2
       The input can be in any time order. For example: [(20, 60, 3), (3, 8, 2)]
       The workload will "add up", so a 3 and 2 will add up to 5

Output: a boolean returning whether the series of workload can fit in without
        exceeding MaxWorkLoad

dict[beginTime] ||= 0;    // if not defined, then set it to 0
dict[beginTime] += workload;

dict[endTime] ||= 0;
dict[endTime] -= workload;