Recall & Review
beginner
What is the main goal of the Merge Overlapping Intervals problem?
To combine all intervals that overlap into a single continuous interval, so no two intervals overlap in the final list.
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beginner
Why do we sort intervals by their start time before merging?
Sorting by start time helps us easily find overlapping intervals by checking consecutive intervals only, making the merging process simple and efficient.
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intermediate
In merging intervals, what does it mean if the current interval's start is less than or equal to the last merged interval's end?
It means the intervals overlap and should be merged by extending the last merged interval's end to the maximum end of both intervals.
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beginner
What data structure is commonly used to store merged intervals during the process?
A dynamic array or list is used to store merged intervals as we build the final set of non-overlapping intervals.
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beginner
Show the result of merging intervals: [[1,3], [2,6], [8,10], [15,18]]
After merging overlapping intervals, the result is [[1,6], [8,10], [15,18]]. The first two intervals overlap and merge into [1,6].
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What is the first step in merging overlapping intervals?
✗ Incorrect
Sorting intervals by their start time helps to easily identify overlapping intervals in order.
If interval A is [1,5] and interval B is [4,8], what should the merged interval be?
✗ Incorrect
Since intervals overlap, merge by taking the minimum start (1) and maximum end (8).
When do you add a new interval to the merged list without merging?
✗ Incorrect
If current interval starts after the last merged interval ends, they do not overlap and can be added separately.
What is the time complexity of merging intervals after sorting?
✗ Incorrect
Sorting takes O(n log n), and merging intervals in one pass takes O(n), so total is O(n log n).
Which of these intervals overlap with [3,7]?
✗ Incorrect
Interval [5,10] overlaps with [3,7] because 5 ≤ 7.
Explain the step-by-step process to merge overlapping intervals.
Think about sorting first and then comparing intervals one by one.
You got /6 concepts.
Describe how to check if two intervals overlap and how to merge them.
Focus on start and end points comparison.
You got /3 concepts.