Develop a program to reverse a linked list iteratively and recursively in C

#include <stdio.h>

#include <stdlib.h>

// Structure for a node in the singly linked list

struct Node {

    int data;

    struct Node* next;

};

// Function to create a new node

struct Node* createNode(int data) {

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

    if (newNode == NULL) {

        printf("Memory allocation failed!\n");

        exit(1);

    }

    newNode->data = data;

    newNode->next = NULL;

    return newNode;

}

// Function to insert a node at the end of the list

void insertAtEnd(struct Node** head, int data) {

    struct Node* newNode = createNode(data);

    if (*head == NULL) {

        *head = newNode;

        return;

    }

    struct Node* temp = *head;

    while (temp->next != NULL) {

        temp = temp->next;

    }

    temp->next = newNode;

}

// Function to display the linked list

void displayList(struct Node* head) {

    if (head == NULL) {

        printf("List is empty\n");

        return;

    }

    printf("Linked List: ");

    struct Node* temp = head;

    while (temp != NULL) {

        printf("%d -> ", temp->data);

        temp = temp->next;

    }

    printf("NULL\n");

}

// Iterative function to reverse the linked list

void reverseIterative(struct Node** head) {

    struct Node *prev = NULL, *current = *head, *next = NULL;

    while (current != NULL) {

        // Store next

        next = current->next;

        // Reverse current node's pointer

        current->next = prev;

        // Move pointers one position ahead

        prev = current;

        current = next;

    }

    *head = prev;

    printf("Linked list reversed iteratively\n");

}

// Recursive function to reverse the linked list

struct Node* reverseRecursiveUtil(struct Node* current, struct Node* prev) {

    if (current == NULL) {

        return prev;

    }

    // Store next

    struct Node* next = current->next;

    // Reverse current node's pointer

    current->next = prev;

    // Recurse for the remaining list

    return reverseRecursiveUtil(next, current);

}

void reverseRecursive(struct Node** head) {

    *head = reverseRecursiveUtil(*head, NULL);

    printf("Linked list reversed recursively\n");

}

// Main function to test the linked list reversal

int main() {

    struct Node* head = NULL;

    // Create a linked list: 10 -> 20 -> 30 -> 40 -> 50

    insertAtEnd(&head, 10);

    insertAtEnd(&head, 20);

    insertAtEnd(&head, 30);

    insertAtEnd(&head, 40);

    insertAtEnd(&head, 50);

    printf("Original ");

    displayList(head);

    // Reverse the linked list iteratively

    reverseIterative(&head);

    displayList(head);

    // Recreate the linked list for recursive reversal

    head = NULL;

    insertAtEnd(&head, 10);

    insertAtEnd(&head, 20);

    insertAtEnd(&head, 30);

    insertAtEnd(&head, 40);

    insertAtEnd(&head, 50);

    printf("\nOriginal ");

    displayList(head);

    // Reverse the linked list recursively

    reverseRecursive(&head);

    displayList(head);

    return 0;

}

Output: