Intervals - Merge Intervals
Consider the following Python code that merges intervals in-place after sorting. Given the input intervals = [[1,4],[2,5],[7,9]], what is the returned list after the function completes?
Consider the following Python code that merges intervals in-place after sorting. Given the input intervals = [[1,4],[2,5],[7,9]], what is the returned list after the function completes?
easy🧾 Code Trace Q12 of Q15
Step-by-Step Solution
Step 1: Sort intervals by start time.
Input is already sorted: [[1,4],[2,5],[7,9]].Step 2: Merge intervals in one pass.
Compare [2,5] with [1,4]: overlap since 2 <= 4, merge to [1,5]. Then compare [7,9] with [1,5]: no overlap, move index forward and assign [7,9]. Final intervals: [[1,5],[7,9]].Final Answer:
Option A -> Option AQuick Check:
Overlapping intervals merged correctly, non-overlapping preserved. [OK]
Quick Trick: Check if current start ≤ last merged end to merge [OK]
Common Mistakes:
MISTAKES- Returning original intervals without merging
- Off-by-one slicing errors
Trap Explanation:
PITFALL- Some candidates forget to slice the list after in-place merge, returning extra intervals.
Interviewer Note:
CONTEXT- Tests ability to mentally execute in-place merging and understand index management.
Master "Merge Intervals" in Intervals
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