What Type of Data Structures Are Stacks?

A stack is a fundamental data structure in computer science. It follows the LIFO (Last-In, First-Out) principle, which means that the last element added to the stack is the first one to be removed. In this article, we will explore different types of data structures that can be implemented using stacks.

Stacks as an Array

One common way to implement a stack is by using an array. In this approach, we allocate a fixed-size array and keep track of the top element in the stack using a variable called “top”.

Whenever we push an element onto the stack, we increment “top” and store the new element at index “top” in the array. Similarly, when we pop an element from the stack, we retrieve it from index “top” and decrement “top”.

Example:

Push:

• Increment “top”
• Store new element at array[top]

Pop:

• Retrieve element from array[top]
• Decrement “top”

Stacks as Linked Lists

An alternative implementation of a stack is using a linked list. In this approach, each node in the linked list represents an element in the stack.

The top of the stack is represented by the head of the linked list. When pushing an element onto the stack, we add a new node at the beginning of the linked list and update the head accordingly. When popping an element from the stack, we remove and return the head node, updating it to point to its next node.

Example:

Push:

• Create a new node
• Set the new node’s next pointer to the current head
• Update the head to point to the new node

Pop:

• Return the value of the current head node
• Update the head to point to its next node

Stacks as Function Call Stack

In addition to being a data structure, stacks are also widely used in programming languages to manage function calls. Whenever a function is called, its return address and local variables are pushed onto the stack. When the function returns, these values are popped from the stack, allowing the program execution to resume from where it left off.

Example:

Function Call:

• Push return address onto the stack
• Push function arguments onto the stack
• Jump to function code

Function Return:

• Pop return address from the stack
• Pop function arguments from the stack (if any)
• Resume execution at return address

In conclusion, stacks can be implemented using arrays or linked lists and have various applications in computer science and programming. Understanding different types of data structures that can be implemented using stacks is essential for designing efficient algorithms and solving complex problems.