Return Finite Gaps Shared by Every Schedule

### Problem schedule contains each employee's sorted, nonoverlapping working intervals. Return all finite, positive-length intervals during which everyone is free, in increasing order. Keep the native Interval objects with start/end fields in both input and output; [a,b] notation below only describes those objects. Omit unbounded outside time and zero-length gaps. ```cpp class Solution { public: vector<Interval> employeeFreeTime(vector<vector<Interval>> schedule); }; ``` ### Examples **Example 1:** ```text schedule = [[[1,3],[7,9]],[[2,5]]] Output intervals: [[5,7]] Explanation: Someone is busy throughout [1,5] and [7,9]. ``` **Example 2:** ```text schedule = [[[0,2]],[[2,4]]] Output intervals: [] Explanation: Touching work intervals leave no positive-length common gap. ``` ### Constraints - Employee count and intervals per employee are each between 1 and 50. - Each work interval has 0 <= start < end <= 100000000. - Each employee's intervals are sorted and do not overlap. ### Contract considerations Preserve `vector<vector<Interval>>` and `vector<Interval>`, with sorted finite outputs. ```hint Read the boundary condition When is a gap outside the union of every employee's work? ``` ### Boundary reminders Preserve `vector<vector<Interval>>` and `vector<Interval>`, with sorted finite outputs.