stack2.c

//stack using link list using double pointer 

#include <stdio.h>
#include <stdlib.h>

// Define the structure for a stack node
struct Node {
    int data;
    struct Node* next;
};

// Function to push an element onto the stack
void push(struct Node** top, int value) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    if (!newNode) {
        printf("Stack Overflow\n");
        return;
    }
    newNode->data = value;
    newNode->next = *top;
    *top = newNode;
    printf("%d pushed onto the stack\n", value);
}

// Function to pop an element from the stack
int pop(struct Node** top) {
    if (*top == NULL) {
        printf("Stack Underflow\n");
        return -1;
    }
    struct Node* temp = *top;
    int value = temp->data;
    *top = (*top)->next;
    free(temp);
    return value;
}

// Function to peek the top element of the stack
int peek(struct Node* top) {
    if (top == NULL) {
        printf("Stack is empty\n");
        return -1;
    }
    return top->data;
}

// Function to display the elements of the stack
void display(struct Node* top) {
    if (top == NULL) {
        printf("Stack is empty\n");
        return;
    }
    printf("Stack elements are: ");
    while (top != NULL) {
        printf("%d ", top->data);
        top = top->next;
    }
    printf("\n");
}

int main() {
    struct Node* top = NULL;
    int choice, value;

    while (1) {
        printf("\n1. Push\n2. Pop\n3. Display\n4. Peek\n5. Exit\nEnter your choice: ");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                printf("Enter value to push: ");
                scanf("%d", &value);
                push(&top, value);
                break;

            case 2:
                value = pop(&top);
                if (value != -1) {
                    printf("Popped element: %d\n", value);
                }
                break;

            case 3:
                display(top);
                break;

            case 4:
                value = peek(top);
                if (value != -1) {
                    printf("Top element is: %d\n", value);
                }
                break;

            case 5:
                exit(0);

            default:
                printf("Invalid choice, please try again.\n");
        }
    }

    return 0;
}