| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 181 | Group Students by Grade | Medium | HashingHashMapGrouping |
| 182 | Set Operations Implementer | Medium | SetsSetLogic |
| 183 | Consistent Hashing Demo | Medium | HashingHashMapAlgorithm |
| 184 | Cache with Expiry | Medium | HashingHashMapTime |
| 185 | Bloom Filter | Medium | HashingBit ArrayHash |
| 186 | Count Distinct in Windows | Medium | HashingHashMapSliding Window |
| 187 | Frequency-Matched Strings | Medium | HashingHashMapString |
| 188 | Rabin-Karp String Search | Medium | HashingStringRolling Hash |
| 189 | Bank Account System | Medium | OOP DesignClassEncapsulation |
| 190 | Library Management System | Medium | OOP DesignClassCollections |
| 191 | Parking Lot Simulator | Medium | OOP DesignClassLogic |
| 192 | Event Scheduler | Medium | OOP DesignClassPriority Queue |
| 193 | Chat Room System | Medium | OOP DesignClassObserver Pattern |
| 194 | File System Simulator | Medium | OOP DesignClassTree |
| 195 | Vending Machine | Medium | OOP DesignClassState Machine |
| 196 | Rate Limiter | Medium | OOP DesignClassSliding Window |
| 197 | Command Pattern Calculator | Medium | OOP DesignDesign PatternStack |
| 198 | Observable Data Store | Medium | OOP DesignDesign PatternCallbacks |
| 199 | Builder Pattern Config | Medium | OOP DesignDesign PatternFluent API |
| 200 | Strategy Pattern Sorter | Medium | OOP DesignDesign PatternPolymorphism |