# 759. Employee Free Time

## Description

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.

**Example 2:**

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

**Constraints:**

`1 <= schedule.length , schedule[i].length <= 50`

`0 <= schedule[i].start < schedule[i].end <= 10^8`