C Program for Singly Linked List with Insertion and Deletion

#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;

}

// Insertion at the beginning

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

    struct Node* newNode = createNode(data);

    newNode->next = *head;

    *head = newNode;

    printf("Inserted %d at the beginning\n", data);

}

// Insertion at the end

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

    struct Node* newNode = createNode(data);

    if (*head == NULL) {

        *head = newNode;

        printf("Inserted %d at the end\n", data);

        return;

    }

    struct Node* temp = *head;

    while (temp->next != NULL) {

        temp = temp->next;

    }

    temp->next = newNode;

    printf("Inserted %d at the end\n", data);

}

// Insertion after a given node (by value)

void insertAfter(struct Node* head, int afterData, int data) {

    struct Node* temp = head;

    while (temp != NULL && temp->data != afterData) {

        temp = temp->next;

    }

    if (temp == NULL) {

        printf("Node with data %d not found\n", afterData);

        return;

    }

    struct Node* newNode = createNode(data);

    newNode->next = temp->next;

    temp->next = newNode;

    printf("Inserted %d after %d\n", data, afterData);

}

// Deletion of the first node

void deleteFirst(struct Node** head) {

    if (*head == NULL) {

        printf("List is empty\n");

        return;

    }

    struct Node* temp = *head;

    *head = (*head)->next;

    printf("Deleted %d from the beginning\n", temp->data);

    free(temp);

}

// Deletion of the last node

void deleteLast(struct Node** head) {

    if (*head == NULL) {

        printf("List is empty\n");

        return;

    }

    if ((*head)->next == NULL) {

        printf("Deleted %d from the end\n", (*head)->data);

        free(*head);

        *head = NULL;

        return;

    }

    struct Node* temp = *head;

    while (temp->next->next != NULL) {

        temp = temp->next;

    }

    printf("Deleted %d from the end\n", temp->next->data);

    free(temp->next);

    temp->next = NULL;

}

// Deletion of a node with a specific value

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

    if (*head == NULL) {

        printf("List is empty\n");

        return;

    }

    if ((*head)->data == data) {

        struct Node* temp = *head;

        *head = (*head)->next;

        printf("Deleted %d\n", data);

        free(temp);

        return;

    }

    struct Node* temp = *head;

    while (temp->next != NULL && temp->next->data != data) {

        temp = temp->next;

    }

    if (temp->next == NULL) {

        printf("Node with data %d not found\n", data);

        return;

    }

    struct Node* nodeToDelete = temp->next;

    temp->next = nodeToDelete->next;

    printf("Deleted %d\n", data);

    free(nodeToDelete);

}

// 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");

}

// Main function to test the linked list operations

int main() {

    struct Node* head = NULL;

    // Insert some nodes

    insertAtEnd(&head, 10);

    insertAtEnd(&head, 20);

    insertAtEnd(&head, 30);

    displayList(head);

    // Insert at the beginning

    insertAtBeginning(&head, 5);

    displayList(head);

    // Insert after a node

    insertAfter(head, 20, 25);

    displayList(head);

    // Delete operations

    deleteFirst(&head);

    displayList(head);

    deleteLast(&head);

    displayList(head);

    deleteByValue(&head, 20);

    displayList(head);

    return 0;

}

Output: