Introduction to Data Structures
What is a Data Structure?
A data structure is a way of organizing, storing, and managing data in a computer so that it can be accessed and modified efficiently. Think of it like a container — different containers are suited for different purposes. A bookshelf organizes books differently than a stack of plates or a queue at a ticket counter.
Choosing the right data structure is one of the most important decisions in programming. The same problem solved with the wrong data structure can be 1000× slower than with the right one.
Why Learn Data Structures?
- Performance — the right structure makes operations fast (O(1) vs O(n))
- Memory efficiency — store data without wasting space
- Problem solving — most algorithms are built on data structures
- Interviews — data structures are the #1 topic in technical interviews at top companies
- Real-world systems — databases, operating systems, compilers all rely on them
Types of Data Structures
| Category | Data Structures | Key Property |
|---|
| Linear | Array, Linked List, Stack, Queue, Deque | Elements arranged sequentially |
| Non-Linear | Tree, Graph, Heap, Trie | Elements in hierarchical/network form |
| Hash-based | Hash Table, Hash Map, Hash Set | Key-value pairs with O(1) average access |
Operations on Data Structures
| Operation | Description |
|---|
| Traversal | Visit each element once |
| Search | Find a specific element |
| Insertion | Add a new element |
| Deletion | Remove an element |
| Sorting | Arrange elements in order |
| Merging | Combine two structures |
Complexity Quick Reference
| Data Structure | Access | Search | Insert | Delete |
|---|
| Array | O(1) | O(n) | O(n) | O(n) |
| Linked List | O(n) | O(n) | O(1) | O(1) |
| Stack / Queue | O(n) | O(n) | O(1) | O(1) |
| Hash Table | N/A | O(1) avg | O(1) avg | O(1) avg |
| Binary Search Tree | O(log n) | O(log n) | O(log n) | O(log n) |
| Heap | O(1) top | O(n) | O(log n) | O(log n) |