Copy the linked list which has the random pointer and it points to any node in linked list .

The solution is to use copy-merge-split . First copy the nodes and create a new list . Then merge the nodes into the original list .Assume that ur original list is 1->2->3->NULL and u have copied the list and merged it into the orginal list . so the list will look like this 1->1->2->2->3->3->NULL . Then for the random pointer , the even nodes random pointer should point to the odd node's random->next pointer . Then separate the odd and even nodes .

Code is given below . Please let me know if there is any mistake in the code .

Code :(in C)
The node structure is given below .
struct node
{
int data;
struct node* next;
struct node* random;
}

struct node* copy_list_with_random_pointer(struct node * head)
{
//copy list and don't worry about random pointer now
struct node* copied_list_head=copy_list(head);
if(copied_list_head==NULL)
return NULL;
//merge the copied list into original list
struct node* original_list,copied_list,temp,temp1;
original_list=head;
copied_list=copied_list;
while(original_list!=NULL)
{
temp=original_list;
original_list=original_list->link;
temp->link=copied_list;

temp1=copied_list;
copied_list=copied_list->link;
temp1->link=original_list;
}

//set the random pointer for copied list
temp=head;
while(temp!=NULL)
{
temp->link->random=temp->random->next;
temp=temp->link->link;
}
 
       //split the list
original_list=head;
copied_list=head->link;
while(original_list!=null)
{
original_list->link=copied_list->link;
original_list=copied_list->link;
if(original_list!=NULL)
{
copied_list->link=original_list->link;
copied_list=original_list->link;
}
else
copied_list->link=NULL;

}

return copied_list_head;
}

//function to copy the the linked list
struct node* copy_list(struct node * head)
{
if(head==NULL)
return NULL;
struct node* temp,new_head=NULL,tail=NULL;
temp=head;
while(temp!=NULL)
{
struct node* node=malloc(sizeof(struct node*));
if(new_head==NULL)
new_head=node;
if(tail!=NULL)
tail->link=node;

               tail=node;

node->data=temp->data;
temp=temp->link;
}
tail->link=null;
return new_head;
}