← Back to Index

📚 Employee Free Time – Java Cheat Sheet (One Page)

📌 What Is It?

The Employee Free Time problem involves finding the common free time intervals across multiple employees' schedules. Each employee's schedule is represented as a list of non-overlapping intervals.

🧱 Pattern Template

public List employeeFreeTime(List> schedule) {
    List allIntervals = new ArrayList<>();
    for (List employee : schedule) {
        allIntervals.addAll(employee);
    }

    // Sort intervals by start time
    allIntervals.sort((a, b) -> Integer.compare(a.start, b.start));

    List freeTime = new ArrayList<>();
    Interval prev = allIntervals.get(0);

    for (int i = 1; i < allIntervals.size(); i++) {
        Interval curr = allIntervals.get(i);
        if (prev.end < curr.start) {
            // Gap found
            freeTime.add(new Interval(prev.end, curr.start));
        }
        prev = prev.end >= curr.end ? prev : curr;
    }

    return freeTime;
}

✅ Use Cases

📘 Common LeetCode Problems

🧪 Example: Employee Free Time

Input: schedule = [[[1,2],[5,6]],[[1,3]],[[4,10]]]
Output: [[3,4]]
Explanation: There is a free time gap between [3,4].

💡 Pro Tips