SLINK

#include<stdio.h>
#include<stdlib.h>
struct node
{
    int data;
    struct node* link;
};
struct node* head=NULL;
void insert();
void delet();
void display();
void insertfront(int);
void insertposition(int);
void insertlast(int);
void deletefront();
void deleteposition();
void deletelast();

int main()
{
    int choice;
    while(1)
    {
        printf("\n1.insert \n2.delete \n3.display \n4.exit\n");
        printf("enter the choice: ");
        scanf("%d",&choice);
        switch(choice)
        {
            case 1: insert();
                    break;
            case 2: delet();
                    break;
            case 3: display();
                    break;
            case 4: exit(0);
            default : printf("!!invalid option!!");
        }
    }
    return(0);
}

void insert()
{
    int option,data;
    printf("enter the data: ");
    scanf("%d",&data);
    printf("\n1.insert at front \n2.insert at position \n3.insert at last\n");
    printf("enter the option: \n");
    scanf("%d",&option);
    switch(option)
    {
        case 1: insertfront(data);
                break;
        case 2: insertposition(data);
                break;
        case 3: insertlast(data);
                break;
        default:printf("invalid option!!");
    }
}

void insertfront(int data)
{
    struct node* newnode;
    newnode=(struct node*)malloc(sizeof(struct node));
    newnode->link=head;
    newnode->data=data;
    head=newnode;
}

void insertposition(int data)
{
    int i,n;
    struct node* newnode,* temp=head;
    newnode=(struct node*)malloc(sizeof(struct node));
    printf("enter the position: ");
    scanf("%d",&n);
    for(i=0;i<n-2;i++)
    {
        temp=temp->link;
    }
    newnode->data=data;
    newnode->link=temp->link;
    temp->link=newnode;
}

void insertlast(int data)
{
    struct node* newnode,* temp=head;
    newnode=(struct node*)malloc(sizeof(struct node));
    newnode->link=NULL;
    newnode->data=data;
    while(temp->link!=NULL)
    {
        temp=temp->link;
    }
    temp->link=newnode;
}

void delet()
{
    int option;
	if(head==NULL)
	{
		printf("!!!LIST IS EMPTY!!!\n");
	}
	else
	{	
		printf("\n1.delete from front \n2.delete from position \n3.delete fom last\n");
		printf("Enter the option: ");
		scanf("%d",&option);
		switch(option)
		{
			case 1: deletefront();
					break;
			case 2: deleteposition();
					break;
			case 3: deletelast();
					break;
			default:printf("invalid option");
    }
	}
}


void deletefront()
{
    struct node*temp=head;
    head=head->link;
    printf("deleted number is %d",temp->data);
	free(temp);
}

void deleteposition()
{
    int i,n;
    struct node*temp=head;
    struct node*ptr=head;
    printf("enter position: ");
    scanf("%d",&n);
    for(i=1;i<n-2;i++)
    {
        temp=temp->link;
    }
	if(temp->link==NULL)
	{
		printf("list less than the position");
		return;
	}
	else{
		
    for(i=1;i<n-1;i++)
    {
        ptr=ptr->link;
    }
    temp->link=ptr->link;
    printf("deleted number is %d",ptr->data);
	free(ptr);
	}
}

void deletelast()
{
    struct node*temp=head;
    struct node*ptr=head;
    while(temp->link!=NULL)
    {
        temp=temp->link;
    }
    while(ptr->link->link!=NULL)
    {
        ptr=ptr->link;
    }
    printf("deleted element is %d",temp->data);
	free(temp);
    ptr->link=NULL;
}
void display()
{
	struct node*tmp;
	if(head==NULL)
	{
		printf("LIST IS EMPTY\n");
	}
	tmp=head;
	printf("THE LIST IS:");
	while(tmp!=NULL)
	{
		printf("%d",tmp->data);
		tmp=tmp->link;
	}
	printf("\n");
}