Stacks

In the world of programming and data structures, a stack is a last-in, first-out (LIFO) abstract data type. It is an ordered collection of elements where the addition or removal of elements takes place at the same end, called the top.

Implementation of Stacks

One common way to implement a stack is by using an array. The top element of the stack is always at the highest index of the array. When adding elements to the stack, the top index is incremented, and when removing elements, the top index is decremented. Here's an example of a stack implementation using Java:

1%code%

In the example above, we create a stack using the Stack class from the Java Standard Library. We push elements onto the stack using the push method, and pop elements from the stack using the pop method. The empty method is used to check if the stack is empty.

Common Operations on Stacks

1. Push: Adds an element to the top of the stack.
2. Pop: Removes and returns the top element from the stack.
3. Peek: Returns the top element of the stack without removing it.
4. isEmpty: Checks if the stack is empty.

Stacks are useful in various algorithms and data structures. For example, they can be used in backtracking algorithms, expression evaluation, and graph algorithms.

Now that you have a basic understanding of stacks, let's move on to the next topic: Queues.

xxxxxxxxxx

class Main {

  public static void main(String[] args) {

    // replace with your Java logic here

    // Example of a stack implementation

    Stack<Integer> stack = new Stack<>();

​

    // Push elements onto the stack

    stack.push(1);

    stack.push(2);

    stack.push(3);

​

    // Pop elements from the stack

    while (!stack.empty()) {

      System.out.println(stack.pop());

    }

  }

}