What are the differences between a linked list and a stack?

In computer science, a linked list is a dynamic data structure that is composed of nodes. Each node consists of data and a reference to the next node, creating a sequence that can efficiently be adjusted by inserting or deleting nodes. Unlike arrays, linked lists do not have a fixed size and their elements are not stored in contiguous memory locations, which makes them particularly useful for situations where the data size may change frequently.

For example, suppose you are keeping track of the players in an online game where players can join and leave at any moment. A linked list allows you to easily update this list without reallocating the whole data structure. Consider a simple node structure in a singly linked list, represented as:

• Node(data, next)

For instance, to add a player, you create a new node and adjust the 'next' links without the need to shift elements as in an array.

To further enhance understanding, envision the linked list as a train with multiple carriages connected to each other. Each carriage (node) has a unique passenger (data) and a direct link to the next carriage in line (next node). This structure affords each passenger the freedom to embark or disembark (insertion/deletion) at various points, without requiring the entire train to rearrange.

A stack is a linear and orderly data structure where elements are added or removed following a specific principle known as Last In, First Out (LIFO). Just as in a stack of dishes, you can only add a new dish to the top and remove from the top as well. This simplicity makes the stack structure very efficient in scenarios where this sort of organization is beneficial.

Imagine a pile of books on a desk; you can only effectively place a new book on the top and, when you need a book, you'll take the top one. Translated into programming actions, this would relate to:

• Push: Placing the book on the stack.
• Pop: Taking the top book from the stack.
• Peek (or Top): Checking what the top book is without removing it from the stack.

Stacks are prevalent in many familiar scenarios, such as undo mechanisms in software applications, parsing syntactic elements in compilers, or managing function calls in almost every modern programming language.

The term LIFO, short for Last In, First Out, is a fundamental principle used in various data structures, most prominently in stacks. It refers to the way in which items are retrieved from the structure; the last element that was added is the first one to be removed. This policy is what differentiates stacks from queues, which operate on a First In, First Out (FIFO) basis.

Consider LIFO as similar to stacking coins; the last coin you place on top is the first one you'll need to remove if you're only allowed to take from the top. This principle translates seamlessly to digital data management and serves numerous applications such as making sure that the most recent commands or pages visited in a browser are readily accessible. In programming, this can be encapsulated as:

• When a function is called, it is 'pushed' onto the call stack.
• Upon completion, this function is 'popped' off, returning control to the function that resides on the next level down the stack.

This powerful concept is intuitive yet robust, enabling sophisticated operations like recursive functions and backtracking algorithms.