759. Employee Free Time

We are given a list schedule of employees, which represents the working time for each employee.

Each employee has a list of non-overlapping Intervals , and these intervals are in sorted order.

Return the list of finite intervals representing common, positive-length free time for all employees, also in sorted order.

Example 1:

Input:

 schedule = [[[1,2],[5,6]],[[1,3]],[[4,10]]]
Output:

 [[3,4]]
Explanation:

There are a total of three employees, and all common
free time intervals would be [-inf, 1], [3, 4], [10, inf].
We discard any intervals that contain inf as they aren't finite.

 

Example 2:

Input:

 schedule = [[[1,3],[6,7]],[[2,4]],[[2,5],[9,12]]]
Output:

 [[5,6],[7,9]]

 

(Even though we are representing Intervals in the form [x, y] , the objects inside are Intervals , not lists or arrays. For example, schedule[0][0].start = 1, schedule[0][0].end = 2 , and schedule[0][0][0] is not defined.)

Also, we wouldn't include intervals like [5, 5] in our answer, as they have zero length.

Note:

1. schedule and schedule[i] are lists with lengths in range [1, 50] .
2. 0 <= schedule[i].start < schedule[i].end <= 10^8 .

NOTE:  input types have been changed on June 17, 2019. Please reset to default code definition to get new method signature.