Sort the intervals by their start points, then iterate through them while merging any that overlap with the current merged interval. This approach ensures O(n log n) time due to sorting and O(n) space for the output.
Pro tip: Clarify edge cases upfront, such as empty input, single interval, or intervals that touch (e.g., [1,2] and [2,3]). Mentioning these shows attention to detail and can guide the interviewer's expectations.
Ask clarifying questions about input format, whether intervals are inclusive, and expected output. Confirm edge cases like empty list or single interval.
Sort the list of intervals by their start points. This is crucial for the linear scan approach.
Initialize a result list with the first interval. Iterate through the sorted intervals, and if the current interval overlaps with the last interval in the result, merge them by updating the end point; otherwise, add the current interval to the result.
After processing all intervals, return the merged list, which is already sorted by start point.
State the time complexity O(n log n) due to sorting and space complexity O(n) for the output. Mention that the merging step is O(n).
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