What is the difference between a stack and a linked list?

A stack and a linked list are both data structures used to store and organize data, but they have some key differences.

1. Structure: A stack is a linear data structure that follows the Last-In-First-Out (LIFO) principle, meaning the last element added to the stack is the first one to be removed. On the other hand, a linked list is a collection of nodes where each node contains a data element and a reference (or link) to the next node in the sequence.

2. Operations: Stacks typically support two main operations: push and pop. Push adds an element to the top of the stack, while pop removes the topmost element. Linked lists, on the other hand, support various operations such as insertion, deletion, and traversal. In addition to adding and removing elements, linked lists allow for more flexibility in terms of modifying and accessing data at any position.

3. Memory Allocation: Stacks are usually implemented using arrays, where a fixed amount of memory is allocated. This fixed size can lead to stack overflow if the number of elements exceeds the allocated space. In contrast, linked lists dynamically allocate memory for each node as needed, allowing for more efficient memory usage and flexibility in terms of size.

4. Efficiency: Stacks generally have faster access and insertion times compared to linked lists since they operate on a single end. However, linked lists have better performance for insertion and deletion operations in the middle or at the beginning, as they only require updating the references.

5. Usage: Stacks are commonly used in scenarios where the order of elements is important, such as function calls, expression evaluation, and backtracking algorithms. Linked lists are more versatile and can be used in various scenarios, including implementing other data structures like queues, graphs, and hash tables.

In summary, the main difference between a stack and a linked list lies in their structure, operations, memory allocation, efficiency, and usage. Stacks are simpler and more restricted, while linked lists offer more flexibility and functionality.