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What is the time complexity of the optimal in-place merge intervals algorithm that first sorts the intervals and then merges them in one pass?

medium🪤 Complexity Trap Q5 of Q15
Intervals - Merge Intervals
What is the time complexity of the optimal in-place merge intervals algorithm that first sorts the intervals and then merges them in one pass?
AO(n^2)
BO(n log n)
CO(n)
DO(log n)
Step-by-Step Solution
Solution:
  1. Step 1: Analyze sorting step

    Sorting intervals by start time takes O(n log n) time.
  2. Step 2: Analyze merging step

    Merging intervals in one pass is O(n) time.
  3. Step 3: Combine complexities

    Total time is dominated by sorting: O(n log n) + O(n) -> O(n log n).
  4. Final Answer:

    Option B -> Option B
  5. Quick Check:

    Sorting dominates time complexity [OK]
Quick Trick: Sorting dominates time complexity -> O(n log n) [OK]
Common Mistakes:
MISTAKES
  • Choosing O(n) ignoring sorting
  • Confusing with quadratic due to nested loops
Trap Explanation:
PITFALL
  • Candidates often forget sorting cost and assume linear time due to single pass merge.
Interviewer Note:
CONTEXT
  • Tests understanding of time complexity combining sorting and linear merge.
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