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What is the time complexity of the optimal greedy algorithm that finds the maximum number of non-overlapping intervals by sorting intervals and iterating through them once?

medium🪤 Complexity Trap Q13 of Q15
Intervals - Non-overlapping Intervals (Max Non-Overlap)
What is the time complexity of the optimal greedy algorithm that finds the maximum number of non-overlapping intervals by sorting intervals and iterating through them once?
AO(n log n) due to sorting plus O(n) iteration, total O(n log n)
BO(n^2) due to nested comparisons between intervals
CO(n) since it only iterates once through the intervals
DO(n log n) because of sorting intervals by start or end time
Step-by-Step Solution
  1. Step 1: Identify sorting cost

    Sorting intervals by start or end time takes O(n log n) time.
  2. Step 2: Identify iteration cost

    Iterating through the sorted intervals to select non-overlapping ones takes O(n) time.
  3. Final Answer:

    Option A -> Option A
  4. Quick Check:

    Sorting dominates, total complexity is O(n log n) [OK]
Quick Trick: Sorting dominates time complexity in interval scheduling [OK]
Common Mistakes:
MISTAKES
  • Assuming iteration alone is O(n) and ignoring sorting
  • Mistaking nested loops causing O(n^2)
  • Confusing sorting and iteration costs
Trap Explanation:
PITFALL
  • Option B looks correct but is incomplete; sorting plus iteration is O(n log n), not just sorting alone.
Interviewer Note:
CONTEXT
  • Checks if candidate understands sorting cost dominates greedy interval scheduling.
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