What is the minimum number of meeting rooms needed for overlapping meetings?
This problem tests your ability to apply greedy algorithms and priority queues to resource allocation scenarios. It requires sorting intervals and tracking overlaps efficiently.
Why Interviewers Ask This
Meeting room scheduling is a real-world application of interval management. Interviewers ask this to see if you can optimize resources using efficient data structures. It evaluates your skill in transforming a temporal problem into a computational one using heaps.
How to Answer This Question
Sort the meetings by their start times. Use a min-heap to track the end times of ongoing meetings. Iterate through the sorted meetings, checking if the earliest ending meeting has finished before the current one starts. If so, remove it from the heap and reuse the room; otherwise, allocate a new room. The size of the heap at any point represents the number of rooms needed.
Key Points to Cover
- Sorting by start time
- Using a min-heap for end times
- Greedy assignment logic
- Heap size as room count
Sample Answer
First, sort all meetings based on their start times. Then, initialize a min-heap to keep track of meeting end times. For each meeting, check if its start time is greater than or equal to the smallest end time in the heap. If yes, pop the earliest ending meeting and push the current meeting's end time, effectively reusing that room. If not, push the current meeting's end time, indicating a need for a new room. The maximum size of the heap during this process gives the minimum number of rooms required.
Common Mistakes to Avoid
- Sorting by end time instead of start
- Failing to update the heap correctly
- Not considering overlapping intervals properly
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