Interval task patterns

Interval tasks ask you to reason about ranges on a line: merge overlaps, insert a range, count rooms, find free time, or process start and end events. Sorting by start time often unlocks a one-pass solution; heaps or sweep lines handle active intervals.

Trade-off: compare time, memory, and implementation complexity before committing to a structure or pattern.

On interviews: The key is defining endpoint semantics. Inclusive and exclusive ends change overlap checks, especially for calendars and meeting rooms.

Common pitfalls: Do not merge adjacent intervals unless the requirements say they overlap. Tie-breaking start and end events incorrectly can change active counts.

Checklist:

• Define endpoint semantics.
• Sort by start or event time.
• Maintain active intervals.
• Test touching boundaries.