Linked list

Definition

A linked list is a linear data structure where each element, called a node, contains a value and a reference to the next node in the sequence. This structure allows for efficient insertions and deletions, as nodes can be added or removed without reorganizing the entire data structure. Linked lists can be singly linked, where each node points to the next, or doubly linked, where nodes point to both the next and previous nodes, making traversal easier in both directions.

5 Must Know Facts For Your Next Test

1. Linked lists are dynamic in size, meaning they can grow and shrink as needed, unlike static arrays that have fixed sizes.
2. They provide efficient memory usage since memory allocation is done at runtime and only when necessary.
3. Traversal of linked lists is done sequentially, which can make access times slower compared to arrays since elements are not stored contiguously in memory.
4. Inserting or deleting a node in a linked list can be done in constant time O(1) if you have a reference to the node before it, while finding a node requires O(n) time on average.
5. Linked lists are often used in applications that require frequent insertion and deletion of data elements, such as implementing stacks, queues, and adjacency lists for graphs.

Review Questions

• How does the structure of a linked list allow for efficient insertions and deletions compared to an array?
  • Linked lists allow for efficient insertions and deletions because they do not require shifting elements like arrays do. In a linked list, adding or removing a node involves updating references to connect surrounding nodes directly to each other, which can be done in constant time O(1) if you have access to the appropriate nodes. In contrast, arrays require moving elements to fill gaps after deletion or to create space for new elements, which takes more time.
• What are the differences between singly linked lists and doubly linked lists in terms of traversal and memory usage?
  • Singly linked lists only allow traversal in one direction since each node has a reference only to the next node. This means that traversing backwards is not possible without starting from the head. In contrast, doubly linked lists allow traversal in both directions because each node contains references to both its next and previous nodes. However, this additional reference in doubly linked lists results in slightly higher memory usage per node compared to singly linked lists.
• Evaluate how the characteristics of linked lists influence their use cases in software development, particularly in dynamic applications.
  • Linked lists are particularly beneficial in dynamic applications where data size can change frequently. Their ability to grow and shrink in size without reallocating memory makes them ideal for scenarios such as implementing queues or stacks. Additionally, their efficiency in insertions and deletions is advantageous for real-time applications where speed is essential. However, the trade-off comes with slower access times for elements, which may not be suitable for applications requiring frequent random access. Overall, understanding when to use linked lists versus other data structures like arrays is crucial for optimizing performance based on specific needs.

Related terms

Node: The fundamental part of a linked list that contains data and a reference to the next node.

Singly Linked List: A type of linked list where each node points to only the next node in the sequence.

Doubly Linked List: A type of linked list where each node points to both the next and previous nodes, allowing traversal in both directions.