Linked List

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

struct node{
    int data;
    struct node* next;
};
struct node* head = NULL;
void menu(){
    printf("\n******************");
    printf("\nEnter your choice:\n");
    printf("1. Insert at Beginning\t");
    printf("\t2. Insert at End\t");
    printf("3. Insert at Position\n");
    printf("4. Delete from Beginning\t");
    printf("5. Delete from End\t");
    printf("6. Delete from Position\n");
    printf("7. Display\n");
    printf("0. Exit");
    printf("\n******************\n");
}
void display() {
    if (head == NULL){
        printf("Empty List.\n");
    return;
    }
    struct node* current=head;
    while(current!=NULL){
        printf("%d\t",current->data);
        current=current->next;
    }
}
void insertAtFront(){
    struct node* new_node;
    new_node=(struct node*)malloc(sizeof(struct node));
    printf("Enter Data in new node:");
    scanf("%d",&new_node->data);
    new_node->next=NULL;
    if (head==NULL) {
        head = new_node;
        return;
    }
    new_node->next=head;
    head = new_node;
}
void insertAtEnd(){
    struct node* new_node;
    new_node=(struct node*)malloc(sizeof(struct node));
    printf("Enter Data in new node:");
    scanf("%d",&new_node->data);
    new_node->next=NULL;
    if (head==NULL) {
        head = new_node;
        return;
    }
    struct node* current= head;
    while (current->next!=NULL){
        current=current->next;
    }
    current->next=new_node;
}
void insertAtPos(){
    struct node* new_node;
    new_node=(struct node*)malloc(sizeof(struct node));
    printf("Enter Data in new node:");
    scanf("%d",&new_node->data);
    new_node->next=NULL;
    if (head==NULL){
        printf("Empty list\n");
    }
    int key;
    printf("Enter the key to be searched:");
    scanf("%d",&key);
    if (head->data==key) {
        head->next = new_node;
        return;
    } else {
        struct node* temp = head;
        while (temp!=NULL && temp->data!=key){
            temp=temp->next;
        }
        if(temp==NULL) {
            printf("Key not found in list!\n");
            return;
        }
        new_node->next=temp->next;
        temp->next=new_node;
        printf("Item inserted after %d\n",key);
    }
}
void deleteAtFront(){
    if (head==NULL){
        printf("Empty List!\n");
        return;
    }
    struct node* temp=head;
    head=head->next;
    free(temp);
}
void deleteAtEnd(){
    if (head==NULL){
        printf("Empty List!\n");
        return;
    }
    struct node *temp = head;
    struct node *prev = head;
    if (head->next==NULL)
        head=NULL;
    else {
        while (temp->next != NULL) {
            prev = temp;
            temp = temp->next;
        }
        prev->next = NULL;
    }
    free(temp);
}
void deleteAtPos(){
    int flag=0;
    if (head==NULL){
        printf("Empty List!\n");
        return;
    }
    int key;
    printf("Enter data to be deleted:");
    scanf("%d",&key);
    struct node* temp=head;
    struct node* prev;
    if(head->data==key && head->next==NULL){
        flag=1;
        head=NULL;
    } else if (head->data==key && head->next!=NULL){
        flag=1;
        head=head->next;
    } else{
        while (temp->next!=NULL) {
            prev = temp;
            temp = temp->next;
            if (temp->data==key) {
                flag = 1;
                break;
            }
        }
        if(flag==1){
            prev->next=temp->next;
        }
    }
    if (flag==0) {
        printf("Key not found!");
        return;
    }
    free(temp);
}
int main() {
    int arg;
    while(1){
        menu();
        scanf("%d",&arg);
        switch(arg){
            case 1:
                insertAtFront();
                break;
            case 2:
                insertAtEnd();
                break;
            case 3:
                insertAtPos();
                break;
            case 4:
                deleteAtFront();
                break;
            case 5:
                deleteAtEnd();
                break;
            case 6:
                deleteAtPos();
                break;
            case 7:
                display();
                break;
            case 0:
                exit(0);
            default:
                printf("Invalid Argument!");
                break;
        }
    }
}