Day 4 of DSA in C

Write a menu driven C program to create a single linked list and perform the insertion, deletion and display functions on it.

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


struct Node {
    int data;
    struct Node* next;
};

struct Node* head = NULL;

struct Node* createNode(int value) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = value;
    newNode->next = NULL;
    return newNode;
}

void insertAtBeginning(int value) {
    struct Node* newNode = createNode(value);
    newNode->next = head;
    head = newNode;
    printf("Inserted %d at the beginning.\n", value);
}

void insertAtEnd(int value) {
    struct Node* newNode = createNode(value);
    if (head == NULL) {
        head = newNode;
    } else {
        struct Node* temp = head;
        while (temp->next != NULL)
            temp = temp->next;
        temp->next = newNode;
    }
    printf("Inserted %d at the end.\n", value);
}

void insertAtPosition(int value, int pos) {
    if (pos < 1) {
        printf("Invalid position!\n");
        return;
    }
    if (pos == 1) {
        insertAtBeginning(value);
        return;
    }
    struct Node* newNode = createNode(value);
    struct Node* temp = head;
    for (int i = 1; i < pos - 1 && temp != NULL; i++)
        temp = temp->next;
    if (temp == NULL) {
        printf("Position out of range!\n");
        free(newNode);
    } else {
        newNode->next = temp->next;
        temp->next = newNode;
        printf("Inserted %d at position %d.\n", value, pos);
    }
}

void insertAfterKey(int key, int value) {
    struct Node* temp = head;
    while (temp != NULL && temp->data != key)
        temp = temp->next;
    if (temp == NULL) {
        printf("Key %d not found!\n", key);
        return;
    }
    struct Node* newNode = createNode(value);
    newNode->next = temp->next;
    temp->next = newNode;
    printf("Inserted %d after key %d.\n", value, key);
}

void deleteBeginning() {
    if (head == NULL) {
        printf("List is empty!\n");
        return;
    }
    struct Node* temp = head;
    head = head->next;
    printf("Deleted %d from beginning.\n", temp->data);
    free(temp);
}

void deleteEnd() {
    if (head == NULL) {
        printf("List is empty!\n");
        return;
    }
    if (head->next == NULL) {
        printf("Deleted %d from 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 end.\n", temp->next->data);
    free(temp->next);
    temp->next = NULL;
}

void deletePosition(int pos) {
    if (head == NULL) {
        printf("List is empty!\n");
        return;
    }
    if (pos < 1) {
        printf("Invalid position!\n");
        return;
    }
    if (pos == 1) {
        deleteBeginning();
        return;
    }
    struct Node* temp = head;
    for (int i = 1; i < pos - 1 && temp != NULL; i++)
        temp = temp->next;
    if (temp == NULL || temp->next == NULL) {
        printf("Position out of range!\n");
    } else {
        struct Node* del = temp->next;
        temp->next = del->next;
        printf("Deleted %d from position %d.\n", del->data, pos);
        free(del);
    }
}

void deleteByKey(int key) {
    if (head == NULL) {
        printf("List is empty!\n");
        return;
    }
    if (head->data == key) {
        struct Node* temp = head;
        head = head->next;
        printf("Deleted node with key %d.\n", key);
        free(temp);
        return;
    }
    struct Node* temp = head;
    while (temp->next != NULL && temp->next->data != key)
        temp = temp->next;
    if (temp->next == NULL) {
        printf("Key %d not found!\n", key);
    } else {
        struct Node* del = temp->next;
        temp->next = del->next;
        printf("Deleted node with key %d.\n", key);
        free(del);
    }
}

void display() {
    if (head == NULL) {
        printf("List is empty!\n");
        return;
    }
    struct Node* temp = head;
    printf("Linked List: ");
    while (temp != NULL) {
        printf("%d -> ", temp->data);
        temp = temp->next;
    }
    printf("NULL\n");
}

int main() {
    int choice, value, pos, key;
    while (1) {
        printf("\n---- MENU ----\n");
        printf("1. Insert at Beginning\n");
        printf("2. Insert at End\n");
        printf("3. Insert at Position\n");
        printf("4. Insert After a Key\n");
        printf("5. Delete from Beginning\n");
        printf("6. Delete from End\n");
        printf("7. Delete from Position\n");
        printf("8. Delete by Key\n");
        printf("9. Display\n");
        printf("10. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                printf("Enter value: ");
                scanf("%d", &value);
                insertAtBeginning(value);
                break;
            case 2:
                printf("Enter value: ");
                scanf("%d", &value);
                insertAtEnd(value);
                break;
            case 3:
                printf("Enter value and position: ");
                scanf("%d %d", &value, &pos);
                insertAtPosition(value, pos);
                break;
            case 4:
                printf("Enter key and value: ");
                scanf("%d %d", &key, &value);
                insertAfterKey(key, value);
                break;
            case 5:
                deleteBeginning();
                break;
            case 6:
                deleteEnd();
                break;
            case 7:
                printf("Enter position: ");
                scanf("%d", &pos);
                deletePosition(pos);
                break;
            case 8:
                printf("Enter key: ");
                scanf("%d", &key);
                deleteByKey(key);
                break;
            case 9:
                display();
                break;
            case 10:
                printf("Exiting...\n");
                exit(0);
            default:
                printf("Invalid choice! Try again.\n");
        }
    }
    return 0;
}