| ID | Title | Difficulty |
|---|---|---|
| 218 | The Skyline Problem | Hard |
| 391 | Perfect Rectangle | Hard |
| 850 | Rectangle Area II | Hard |
| 1851 | Minimum Interval to Include Each Query | Hard |
| ID | Title | Difficulty |
|---|---|---|
| 218 | The Skyline Problem | Hard |
| 391 | Perfect Rectangle | Hard |
| 850 | Rectangle Area II | Hard |
| 1851 | Minimum Interval to Include Each Query | Hard |