Given the final merged intervals [[1,6],[8,10],[15,18]] from an unknown input, which of the following could NOT be the original input intervals?

hard🔄 Reverse Engineer Q9 of Q15

Intervals - Merge Intervals

A[[1,6],[8,10],[15,18]]

B[[1,3],[2,6],[8,10],[15,18]]

C[[1,4],[5,6],[8,10],[15,18]]

D[[1,2],[3,5],[8,10],[15,18]]

Step-by-Step Solution

Solution:

Step 1: Understand merged intervals
The merged intervals [[1,6],[8,10],[15,18]] imply overlapping intervals in the original input that merged into [1,6].
Step 2: Analyze each option
[[1,6],[8,10],[15,18]] is already merged; it cannot be the original input because original inputs are usually unmerged intervals.
Step 3: Verify other options
Options A, C, and D contain intervals that merge to [1,6], so they are plausible original inputs.
Final Answer:
Option A -> Option A
Quick Check:
Original input must have overlapping intervals to merge [OK]

Quick Trick: Original input must have overlapping intervals to merge [OK]

Common Mistakes:

MISTAKES

Trap Explanation:

PITFALL

Candidates confuse merged output with possible original inputs, missing that original must have overlaps.

Interviewer Note:

CONTEXT

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