ll.cpp

#include <bits/stdc++.h>
using namespace std;
#define endl '\n'

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

node* InsertAtHead(node* head,int x)
{
	node* temp = new node();
	temp->data =x;
	temp->next=head;
	head =temp;
	return head;
}

void print_list(node* head)
{
	while(head!=NULL)
	{
		cout<<head->data<<endl;
		head=head->next;
	}
	return;
}

node* InsertAtEnd(node* head,int x)
{
	node* temp = new node();
	temp->data = x;
	temp->next=NULL;
	node* temp1 = head;
	while(temp1->next!=NULL)
		temp1 = temp1->next;
	temp1->next = temp;
	return head;
}

node* InsertAtPos(node* head,int x,int n)
{
	node* temp = new node();
	temp->data = x;
	temp->next=NULL;

	//if one has to insert at the front
	if(n==1)
	{
		temp->next = head;
		head=temp;
		return head;
	}
	//iterate to (n-1)th position
	node* temp1 = head;
	for(int i=1;i<(n-1);i++)
		temp1 = temp1->next;
	temp->next= temp1->next;
	temp1->next=temp;
	return head;
}

int main()
{
    
    node* head = NULL;                  //head pointer initially set to NULL
    head = InsertAtHead(head,5);        // list now is: 5->NULL
    head = InsertAtHead(head,18);       // list now is: 18->5->NULL
    head = InsertAtHead(head,50);       // list now is: 50->18->5->NULL
    head = InsertAtHead(head,15);       // list now is: 15->50->18->5->NULL
    print_list(head);
    cout<<endl;
    head = InsertAtEnd(head,20);        // list now is: 15->50->18->5->20->NULL
    head = InsertAtEnd(head,11);        // list now is: 15->50->18->5->20->11->NULL
    print_list(head);
    cout<<endl;
    
    head = InsertAtPos(head,12,4);       // list now is: 15->50->18->12->5->20->11->NULL
    print_list(head);
    cout<<endl;
    return 0;
}