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.
(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.
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.
1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1
|--| |--|
1, 0 -1 0 1 0 -1 0 0 0 0
|-----|
2, 0 -1 -1 1 0 -1 0 0 0 0
|-----------------|
2, 0 -1 0 1 0 -1 0 0 0 -1
2 2 1 1 2 2 1 1 1 1 0
^^^^Example 2:
Input: schedule = [[[1,3],[6,7]],[[2,4]],[[2,5],[9,12]]]
Output: [[5,6],[7,9]]
1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3
|-----| |--|
1 0 0 -1 0 1 0 -1 0 0 0 0, 0
|-----|
1 1 0 -1 -1 1 0 -1 0 0 0 0, 0
|--------| |--------|
1 2 0 -1 -1 0 0 -1 1 0 0 0 -1
1 3 3 2 1 1 1 0 1 1 1 1 0
^^^^ ^^^^^^^
Constraints:
1 <= schedule.length , schedule[i].length <= 500 <= schedule[i].start < schedule[i].end <= 10^8