You must be familiar with data structures in order to store and process data if you want to work in software development. Stacks and queues in a data structure that you will encounter in a variety of challenging situations. In this article will also look into how many stacks are needed to implement a queue and stack vs queue. to understand when to use which data structure, you must first understand the differences between the two.

## STACK

Stack is analogous to stack as a method of arranging items in the real world. Stack is a linear data structure that, like arrays and linked lists, restricts element random access. You can access the items in arrays or linked lists using traversal or random indexing, but the stack data structure does not. A stack is a collection of books stacked on top of one another. Only the top end of these volumes can be stacked on top of each other.

### Stacks Representation

To carry out its operations, the stack data structure uses the Last In First Out or First In Last Out principles. To put it another way, the stack data structure removes the last inserted element from the topmost position first, followed by the first inserted element. As a result, this data structure only requires one pointer to remember the top-most element.

### Basic Stacking Operations

Stacks and Queues can both execute some basic tasks, such as storing and altering data components. The functionalities of the stack will now be clear to you.

On the stacks, you can execute the following operations:

#### 1. push(arg):

During this phase, the components are added to the top of the stack. To put something into a stack, you must pass an element to the Push() method.

The following steps are involved in a push operation:

Step 1 | Determines whether or not the stack is complete. |

Step 2 | If the stack is full, it will quit, resulting in an overflow. |

Step 3 | If the stack isn’t full, it adds one to the top and moves to the next spot. |

Step 4 | Inserts a data element into that area. |

Step 5 | It is declared a success. |

#### 2. Pop ():

An element at the top of the stack is eliminated with this action. There are no parameters required for the pop() function.

The following are some of the steps involved in the pop operation:

Step 1 | Determines whether or not the stack is empty. |

Step 2 | The stack departs if it is already empty, resulting in an underflow condition. |

Step 3 | If the stack is not empty, the highest data element is accessed. |

Step 4 | Decreases the top’s value by one. |

Step 5 | A success is returned. |

#### 3. Peek ():

This method retrieves the stack’s topmost data element without removing it from the data elements.

#### 4. isfull():

This operation determines whether the stack is full or not.

#### 5. isempty():

The isEmpty method determines whether or not the stack is empty.

These operations are required for a** **full stack development**.**

### Implementation of Stacks

- The stack is created using arrays in the static implementation. Static implementation, while simple, is not a flexible method of creation because the size of the stack must be declared during program design, and the size cannot be changed after that. Furthermore, static implementation is inefficient in terms of memory usage. Because an array (to implement stack) is declared before the action begins (at program design time).

- On the other hand, if there are more elements to be stored in the stack, we won’t be able to extend the array’s capacity to accommodate more elements by changing the size of the array. The stack kind of data structure is implemented via pointers in dynamic implementation, also known as linked list representation.

Stacks and Queues are used for a variety of computing tasks. The uses of stacks will now be discussed in this article.

- The stacks are used to evaluate expressions.
- The stacks are used to examine expressions for parenthesis.
- Stacks can also be used to track backward.
- The best application of stacks is the Hanoi Tower.
- Stacks are used to manage memory and perform functions.
- The stacks are also used to reverse strings.

## QUEUE

Queue and stack have a similar data structure with some insertion and deletion restrictions. In a queue, insertion happens at one end and removal happens at the other (opposite) end.

The queue data structure can be better understood by using a real-life illustration of a movie ticket counter. The person who arrives first at a movie ticket desk is always serviced first. And the customer who arrives last will almost certainly be the last to be served. Both endpoints of these queues are open and can perform various tasks. The food court line’s back end inserts a customer, while the front end removes him after providing the service he requested.

The deletion is carried out by another end, which is referred to as the front end. The technical terminology for insertion and deletion in Queue are enqueued () and dequeue(), respectively, whereas the technical words for insertion and deletion in the stack are push() and pop(). Its structure has two pointers, the front pointer, and a rear pointer, with the front pointer pointing to the first element added to the queue and the rear pointer pointing to the last element added to the queue.

### Queues Representation

All of these qualities of a real-world queue are shared by the queue and stack in the data structure. It manipulates data pieces according to the First in First Out principle. The element that is placed first in a list is removed first, according to this principle.

### Basic Procedures

Data manipulation operations can be performed on both stacks and queues, as you’ve seen. Now try to grasp some of the basic functions of the queue data structure that are required to become a full stack web development

- The peek() operation tries to get the data element at the front of the queue without removing it from the queue.
- The isfull() action is used to determine whether or not the queue is full.
- The isempty() action is used to determine whether or not the queue is empty.

#### 1. Enqueue Operation:

It refers to the process of inserting or adding data elements to a queue. You always use the back pointer to insert an element.

Step 1 | Check to see if the line is filled. |

Step 2 | If the queue is already full, quit and create an overflow. |

Step 3 | If the stack isn’t full, increase the back and point to the empty area. |

Step 4 | Insert the data element in the position where the back is pointing. |

Step 5 | Congratulations! |

The REAR and FRONT pointers are used in the enqueue procedure. The steps to do so are as follows and are necessary to learn in full stack web development

#### 2. Dequeue Operation:

Dequeue refers to deleting or removing data components from the queue, which is done with a front pointer.

The steps in the dequeue operation are as follows:

Step 1 | Determine whether or not the queue is empty. |

Step 2 | Determine if the queue is empty and produces an underflow condition. |

Step 3 | If the queue isn’t empty, go to the data where the front is pointing and delete that data element. |

Step 4 | Move the cursor to the next existing data element. |

Step 5 | Confirm your success. |

### Implementation of Queues

To answer the question raised in the beginning how many stacks are needed to implement a queue, now we will find the answer for it

#### 1. Static implementation

Because the size of the array must be stated at design time or before the processing begins, if a queue is created using arrays, the exact amount of elements we want to store in the queue must be assured prior. In this situation, the front of the queue will be the beginning of the array, and the back of the queue will be the end of the array. When utilizing arrays, the following relation gives the total number of elements in the queue:

front + back + 1

If “rear front,” the queue will either have no elements or will always be empty.

#### 2. Dynamic implementation

The fundamental disadvantage of utilizing pointers to create queues is that a node in a linked representation takes up more memory than a matching element in an array representation.

Because each node has at least two fields, one for data and the other for storing the address of the next node, but in linked representation, only one field is used. When inserting or deleting an element in the middle of a collection of other elements, the benefit of using the linked representation becomes clear.

### Queues are of many types

Queue data structures are divided into three categories:

#### 1. Circular Lines

The circular queue’s last node is linked to the first node. Ring Buffer is another name for a circular queue. |

#### 2. Dequeue (Double Ended Queue)

You can conduct insertion and deletion on both the back and front ends of the double-ended queue. |

#### 3. Priority Lines

In the priority queue, each node has a predetermined priority. The first node to be eliminated from the queue is the one with the lowest priority. When a node arrives, it is added to the priority queue. |

### Queues In Practice

CPU and disc scheduling, in which a single resource is shared by multiple users

Data is exchanged asynchronously between two processes via IO Buffers, Files, and Pipes.

- The operating system’s semaphores
- First Come, First Serve (FCFS) scheduling
- In printers, spooling
- In networking, there is a queue in routers and switches.

## Stack vs Queue

The following are some important distinctions between stack and queue:

- The stack is a linear data structure in which elements are entered and deleted from only one end, known as the top, and is based on the LIFO (Last in First Out) principle, which states that the element that was inserted last will be removed first. Queue, on the other hand, is a linear data structure in which elements are added from one end (the back end) and discarded from the other end (the front end). The queue, unlike the stack, works on the FIFO (First In First Out) principle, which implies that things that are inserted first are withdrawn first.
- Pushing data into a stack is known as pushing, whereas enqueuing data into a queue is known as enqueuing.

- Pop refers to a delete operation on a stack, whereas dequeue refers to a delete operation on a queue, a very important full stack web development function.
- Only one pointer is retained in the stack, whereas two pointers are required in the queue.
- The stack data structure is a recursive data structure that is used to solve recursive problems, whereas the queue data structure is a sequential data structure that is used to address problems that need sequential processing.
- The stack can be used to solve problems involving recursion, such as pre-order, post-order, and in-order traversal of the binary tree, whereas the queue can be used to solve problems involving sequential processing of underlying data, such as the producer-consumer dilemma. This is one of the main queue vs stack.
- The stack data structure can be used to tackle problems like string reversal, whereas the queue can be used to construct a thread-safe blocking queue.
- Stacks are a vertical linear collection of components, whereas queues are a horizontal linear collection.
- A real-world example of a stack is a group of dishes stacked one on top of the other, whereas a real-world example of a queue is people standing in line to pay an electricity bill.

Both the stack and the queue stated above are non-primitive abstract data structures that are defined as a collection of components organized in order, although they operate on different principles. Both the stack and the queue are significant data structures because they may be used effectively in a variety of situations.

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