DSA Tutorial

Basic Operations of Stack

The main operations of a stack include:

• Push: Adds an element to the top of the stack.
• Pop: Removes the element from the top of the stack.
• Peek (Top): Returns the top element of the stack without removing it.
• isEmpty: Checks whether the stack is empty.
• isFull: Checks if the stack is full (in case of a fixed-size stack).

Types of Stack

There are several types of stacks based on how the operations are performed:

• Array-Based Stack: A stack implemented using an array.
• Linked List-Based Stack: A stack implemented using a linked list.

Stack Implementation

A stack can be implemented using either an array or a linked list. Here's an example of a stack implementation using an array:

#include 
#define MAX 5

int stack[MAX];
int top = -1;

void push(int value) {
    if (top == MAX - 1) {
        printf("Stack Overflow\n");
    } else {
        top++;
        stack[top] = value;
        printf("Pushed %d\n", value);
    }
}

int pop() {
    if (top == -1) {
        printf("Stack Underflow\n");
        return -1;
    } else {
        int popped = stack[top];
        top--;
        return popped;
    }
}

int peek() {
    if (top == -1) {
        printf("Stack is Empty\n");
        return -1;
    } else {
        return stack[top];
    }
}

int isEmpty() {
    return (top == -1);
}

int main() {
    push(10);
    push(20);
    push(30);
    
    printf("Popped: %d\n", pop());
    printf("Top: %d\n", peek());
    
    return 0;
}
      

Applications of Stack

Stacks have many important applications in computer science, including:

• Expression Evaluation: Stacks are used to evaluate postfix or prefix expressions.
• Function Call Stack: The operating system uses a stack to manage function calls, storing return addresses and local variables.
• Undo/Redo Functionality: Many applications use stacks to implement undo/redo operations.
• Backtracking Algorithms: In problems like maze traversal or pathfinding, stacks are used for backtracking.