LeetCode · Intervals
Intervals Problem Set
Sort by start or end, sweep once, merge or count. Interval problems are greedy at heart — the sort order determines the strategy.
| Difficulty | Pattern | Problem | Key Insight |
|---|---|---|---|
| Medium | merge | LC 56 · Merge Intervals | Sort by start, merge overlapping. O(n log n). |
| Medium | insert | LC 57 · Insert Interval | Find overlap range, merge, collect before/after. O(n). |
| Medium | removal | LC 435 · Non-overlapping Intervals | Sort by end, greedily keep earliest-ending. Remove count = total − kept. O(n log n). |
| Easy | sort | LC 252 · Meeting Rooms | Sort by start, check for any overlap. O(n log n). (Premium) |
| Medium | heap | LC 253 · Meeting Rooms II | Sort by start, min-heap of end times. O(n log n). (Premium) |
| Medium | intersection | LC 986 · Interval List Intersections | Two pointers on sorted interval lists. O(m+n). |
| Medium | covered | LC 1288 · Remove Covered Intervals | Sort by start asc, end desc. Track max end. O(n log n). |
| Hard | heap | LC 2402 · Meeting Rooms III | Two heaps: available rooms + busy rooms. O(m log n). |