Intervals/Employee Free TimeHard

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Employee Free Time

Intervals·Hard

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 (sorted by start), and these intervals are in sorted order by start.

Return the list of finite intervals representing common, positive-length free time for all employees, sorted by start ascending.

(Even though we are representing intervals as [start, end] arrays, the answer should not include intervals of length zero — for example, end-touching busy intervals do not produce a free interval at the touch point.)

Examples

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

Output: [[3,4]]

There are a total of three employees, and all common free time intervals are [-inf, 1], [3, 4], [10, inf]. We discard any infinite intervals and report [[3,4]].

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

Output: [[5,6],[7,9]]

Input: schedule = [[[1,10]]]

Output: []

Constraints

1 <= schedule.length <= 50
1 <= schedule[i].length <= 50
0 <= start < end <= 10^8

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Tests

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Passed32 ms

First attempt — retry to track metric movement here.

Your approach

Pattern:Intervals
Time:O(N)
Space:O(1)

Complete approach — pattern and complexity both named.

Coach

What you got right

You correctly matched the sorted input requirement and implemented a linear-time scan using two pointers.

Where it diverged

No divergence detected. The code correctly aligns with the stated approach.

Next attempt: focus on

Try solving related sliding window problems to build familiarity with two-pointer variants.

Signals

No signals fired — clean run, you stayed in flow.