How To Implement A Stack Using Linked List in C?

#include <stdio.h>

#include <stdlib.h>

#include <conio.h>

#include <limits.h>

struct Node

{

    int data;          // for storing the elements

    struct Node *next; // pointer of the last node

};

struct Node *top = NULL; // points to the first node of the linked list

// Push

void push(int element)

{

    struct Node *newNode = top;

    if (newNode == NULL)

    {

        newNode = (struct Node *)malloc(sizeof(struct Node));

        newNode->data = element;

        newNode->next = NULL;

        top = newNode; // top will point to the recently created node (newNode)

        printf("Element inserted! \n");

    }

    else

    {

        while (newNode->next != NULL)

        { // traversing through the linked list

            newNode = newNode->next;

        }

        // when newNode->next will be equal to NULL, we will come out of the while loop

        struct Node *lastNode = (struct Node *)malloc(sizeof(struct Node));

        newNode->next = lastNode;

        lastNode->data = element;

        lastNode->next = NULL;

        printf("Element inserted! \n");

    }

}

// isEmpty() function to check if the stack is empty

int isEmpty(){

        if(top == NULL){

            return 1;

        }else{

                return 0;

        }

}

// Pop

int pop(){

    struct Node *temp = top;

    int remove;

    if(isEmpty() == 1){

        return INT_MIN;

    }else if(temp->next == NULL){

        remove = top->data;

        free(temp);

        top = NULL;

    }else{

            struct Node *prevNode;

            while(temp->next != NULL){

                    prevNode = temp;

                    temp = temp->next;

            }

            // when we come out of the loop, temp will point to the last node

            remove = temp->data;

            prevNode->next = NULL;

            free(temp);

    }

    return remove;

}

void display(){

    struct Node *temp = top;

    if (temp == NULL)

    {

        printf("Stack is empty !! \n");

    }

    else

    {

        printf("Elements present in the list are : \n");

        while (temp != NULL)

        { // temp will be equal to NULL when we reach the end of the linked list

            if (temp->next != NULL)

                printf("%d ---> ", temp->data);

            else

                printf("%d ---> NULL", temp->data);

            temp = temp->next;

        }

        printf("\n");

    }

}

int main()

{

    int element, position, choice, searchFor, del;

    printf("\t\t STACK IMPLEMENTATION USING LINKED LIST \n");

    do

    {

        printf("\t OPERATIONS \n");

        printf("1. Push \n");

        printf("2. Pop \n");

        printf("3. Display Elements \n");

        printf("4. Exit \n");

        printf("Enter your choice : ");

        scanf("%d", &choice);

        switch (choice)

        {

        case 1:

            printf("Push \n");

            printf("Enter the element you want to insert : ");

            scanf("%d", &element);

            push(element);

            break;

        case 2:

            printf("Pop \n");

            del = pop();

            if (del == INT_MIN)

            {

                printf("Stack is empty!! \n");

            }

            else

            {

                printf("%d removed from the list. \n", del);

            }

            break;

        case 3:

            display();

            break;

        case 4:

            exit(0);

        default:

            printf("Wrong choice entered!! Please enter the correct choice. \n");

            break;

        }

        printf("\nPress enter to continue \n\n");

        getch();

    } while (1);

    return 0;

}

In this program, we have implemented a stack called ‘Node’ of the structure data type using a linked list.

Node has two data members, ‘data’ for storing the elements and ‘next’ which is the reference to the last node in the stack which we have implemented using a linked list.

In the main() function, we have used a switch case to perform operations like push and pop in the stack.

Also, we have defined push(), pop(), isEmpty(), and display() functions to perform the operations on the stack.

Let us look at how the stack is implemented by executing the program.