| Feature | HashSet | TreeSet |
|---|---|---|
| Implementation | Internally uses a hash table. | Internally uses a red-black tree. |
| Ordering | No order; elements are stored randomly. | Maintains ascending order of elements. |
| Duplicates | Does not allow duplicate elements. | Does not allow duplicate elements. |
| Performance | Faster for basic operations like add(), remove(), and contains() (O(1) on average). | Slower for basic operations (O(log n)) due to tree traversal. |
| Null Elements | Allows one null element. | Allows one null element (but in case of a comparator, it might throw exception). |
| Use Case | When you need fast lookup and no specific order. | When you need elements in sorted order. |
| Iteration Order | Iteration order is not predictable. | Iterates in natural order (ascending). |
| Methods | Doesn’t have methods to handle sorting. | Provides methods for range queries, like headSet(), tailSet(). |
| Memory Usage | Less memory overhead as it uses a hash table. | More memory overhead due to the tree structure. |
HashSet:
- No order of elements.
- Faster for most operations.
- Allows null element.
TreeSet:
- Maintains elements in ascending order.
- Slightly slower due to sorting.
- No null if a custom comparator is used.
leetcode samajhdaar wala approach
mandabuddhi wala approach
