| Define and operate on a type represented as a bitfield |  |  |
| Count word frequency in a document |  |  |
| Group records by key | | |
| Look up records within a time range | | |
| Set operations with HashSet | | |
| Use a custom type as a HashMap key | | |
| Look up a tuple key without cloning | | |
| Process tasks in priority order | | |
| Sliding-window buffer with VecDeque | | |