| Problem Type | Input | Output | Complexity | Key Challenge |
|---|---|---|---|---|
| One-to-One | Fixed size | Fixed size | Simple | Feature extraction |
| One-to-Many | Fixed size | Variable sequence | Medium | When to stop generating |
| Many-to-One | Variable sequence | Fixed size | Medium | Sequence aggregation |
| Many-to-Many | Variable sequence | Variable sequence | High | Alignment and length |