# What Is the Concept of Stack in Data Structure?

//

Larry Thompson

What Is the Concept of Stack in Data Structure?

A stack is a fundamental data structure in computer science that follows the Last-In-First-Out (LIFO) principle. It is analogous to a stack of plates, where the last plate added is the first one to be removed. In a stack, elements are added and removed from only one end, known as the top.

## Stack Operations:

A stack supports two primary operations:

• Push: Adds an element to the top of the stack.
• Pop: Removes and returns the topmost element from the stack.

Additionally, there are two more operations that can be performed on a stack:

• Peek: Returns the value of the topmost element without removing it.
• IsEmpty: Checks if the stack is empty or not.

## Stack Implementation:

A stack can be implemented using various data structures, such as arrays or linked lists. Let’s consider an array-based implementation:

``````<pre>
<code>
class Stack {
private int maxSize;
private int[] stackArray;
private int top;

public Stack(int size) {
maxSize = size;
stackArray = new int[maxSize];
top = -1;
}

public void push(int element) {
if (top == maxSize - 1) {
System.out.println("Stack overflow!");
return;
}
stackArray[++top] = element;
}

public int pop() {
if (isEmpty()) {
System.println("Stack underflow!");
return -1;
}
return stackArray[top--];
}

public int peek() {
if (isEmpty()) {
System.println("Stack is empty!");
return -1;
}
return stackArray[top];
}

public boolean isEmpty() {
return (top == -1);
}
}
</code>
</pre>```
```

## Common Applications of Stacks:

Stacks find applications in various areas of computer science. Some common use cases include:

• Expression Evaluation: Stacks are used to evaluate arithmetic expressions, including infix, postfix, and prefix notations.
• Function Call Stack: The function call stack is a stack data structure that keeps track of function calls in a program. It is used for managing function invocations and returning to the calling functions.
• Undo/Redo Functionality: Stacks can be used to implement undo and redo functionality in text editors or graphic applications.
• Backtracking Algorithms: Many backtracking algorithms make use of stacks to store intermediate states and backtrack when necessary.
• Browser History: The browsing history in web browsers can be implemented using a stack. Each visited URL is pushed onto the stack, allowing users to navigate back by popping URLs from the stack.

### In Conclusion:

The concept of a stack plays a vital role in computer science and programming. Understanding its operations and practical applications can greatly enhance your problem-solving abilities. Whether you’re working with algorithms, data structures, or software development in general, having a strong grasp of stacks will undoubtedly benefit you.