Pattern

Intervals

Handle overlapping ranges and scheduling problems.

6 Problems

1 Easy

4 Medium

1 Hard

How Intervals Works

Interval problems involve ranges [start, end] that may overlap, merge, or need scheduling. The universal first step is sorting by start time (or end time for scheduling). After sorting, you scan linearly, comparing each interval's start with the previous interval's end to detect overlaps. For merging, extend the end when overlapping. For insert, find the right position and merge affected intervals. For scheduling, sort by end time and greedily pick non-overlapping intervals.

When to Use Intervals

Pattern Recognition

Look for these trigger words in problem statements:

insert interval intervals merge intervals non-overlapping intervals meeting rooms meeting rooms ii minimum interval to include each query

Common Mistakes

Forgetting to sort the intervals first (almost every interval problem requires sorting)
Sorting by the wrong key (start time for merge, end time for scheduling)
Not handling edge cases: adjacent intervals [1,2],[2,3] — are they overlapping?
Modifying the interval list while iterating instead of building a new result

When NOT to Use Intervals

When intervals have complex dependencies beyond simple overlap
When you need real-time interval insertion/deletion (use an interval tree)
When the problem is about points, not ranges

Practice Problems

Easy (1) Medium (4) Hard (1)

Insert Interval medium Merge Intervals medium Non-overlapping Intervals medium Meeting Rooms easy Meeting Rooms II medium Minimum Interval to Include Each Query hard

Master Intervals

Build pattern recognition with interactive MCQs. Understand why to use Intervals, not just how.

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