Comparison of data structures
This is a comparison of the performance of notable data structures, as measured by the complexity of their logical operations. For a more comprehensive listing of data structures, see List of data structures.
The comparisons in this article are organized by abstract data type. As a single concrete data structure may be used to implement many abstract data types, some data structures may appear in multiple comparisons (for example, a hash map can be used to implement an associative array or a set).
Maps
Maps store a collection of (key, value) pairs, such that each possible key appears at most once in the collection. They generally support three operations:[1]
- Insert: add a new (key, value) pair to the collection, mapping the key to its new value. Any existing mapping is overwritten. The arguments to this operation are the key and the value.
- Remove: remove a (key, value) pair from the collection, unmapping a given key from its value. The argument to this operation is the key.
- Lookup: find the value (if any) that is bound to a given key. The argument to this operation is the key, and the value is returned from the operation.
| Data structure | Lookup, removal | Insertion | Ordered | ||
|---|---|---|---|---|---|
| average | worst case | average | worst case | ||
| Hash table | O(1) | O(n) | O(1) | O(n) | No |
| Self-balancing binary search tree | O(log n) | O(log n) | O(log n) | O(log n) | Yes |
| Unbalanced binary search tree | O(log n) | O(n) | O(log n) | O(n) | Yes |
| Sequential container of key–value pairs (e.g. association list) |
O(n) | O(n) | O(1) | O(1) | No |
Notes
- ^ Mehlhorn, Kurt; Sanders, Peter (2008), "4 Hash Tables and Associative Arrays", Algorithms and Data Structures: The Basic Toolbox (PDF), Springer, pp. 81–98, archived (PDF) from the original on 2014-08-02