LeetCode Card 280 — Intervals / Check
Pattern signal
This pattern usually appears when the prompt involves overlap, merging, scheduling, or span comparison across ranges. Merge Intervals, Insert Interval, Meeting Rooms, and non-overlap optimization are staple cases.
What Check means here
In BASIC, the Check step is where you dry-run the result on edge cases, confirm complexity, and inspect whether the invariant actually held. For Intervals, that matters because the pattern only becomes useful once the candidate is explicit about what is being tracked, reduced, or preserved.
Interview move
A strong move is to review and stress-test before you hand the answer over. In this pattern family, say out loud what representation makes the problem easier: the map entry, the pointer invariant, the recursion contract, the queue contents, or the DP state. That keeps the implementation attached to a reason.
Common miss
The miss is forgetting the ordering step or not being explicit about the overlap condition. BASIC reduces that risk because the stage sequence forces you to earn the implementation instead of jumping straight into it.
BASIC prompt
“Given that this looks like Intervals, what is the simplest way to dry-run the result on edge cases, confirm complexity, and inspect whether the invariant actually held?”