These problems look similar but ask different things:
| Problem | Goal | Approach |
|---|---|---|
| Activity Selection | Max non-overlapping | Sort by end, greedily select |
| Meeting Rooms I | Any overlap? | Sort by start, check adjacent |
| Meeting Rooms II | Min rooms for all | Count max simultaneous |
Recognize which question is being asked. The algorithm changes based on the goal. Mixing them up is a common interview mistake.