Question

C++ PROGRAM/ DLL

• int count(node * head)
recursively compute and return the number of nodes in the doubly linked list.
• void insert(node * & head, int newInt, int position) recursively insert newInt at index “position” where index starts from 0
• int remove(node * & head, int position)
recursively remove the integer at index “position” and return it.

Answer 1

#include<iostream>
#include<cstdlib>
using namespace std;

struct node{ //structure of Doubly Linked List
int data;
struct node *next, *prev;
};

//takes head pointer, newInt val and position of node in DLL
//insert function inserts node in the specified position
//if position is valid else inserts at the end of the DLL
void insert(node* &head, int newInt, int pos)
{
pos -= 1;
if(head==NULL){
node *p = new node;
p->data = newInt;
p->prev = p->next = NULL;
head = p;
return;
}
else if(pos==0){
node *p = new node;
p->data = newInt;
p->next = head;
head->prev = p;
p->prev = NULL;
head = p;
return;
}
else if(head->next==NULL||pos==1){
node *p = new node;
p->data = newInt;
p->prev = head;
p->next = head->next;
head->next = p;
if(head->next)
head->next->prev = p;
return;
}
insert(head->next,newInt,pos);
}

//remove function takes head and position of node to be removed
//if position is valid then removes the node from the DLL and returns the node value
//else return -1
int remove(node* &head,int pos)
{
pos -= 1;
if(head==NULL)
return -1;
else if(pos==1&&head->next){
int data = head->next->data;
node *t = head->next->next;
head->next = t;
if(t)
t->prev = head;
return data;
}
else if(pos==0){
int data = head->data;
if(head->next==NULL)
head = NULL;
else{
node *t = head->next;
t->prev = NULL;
head = head->next;
}
return data;
}
return remove(head->next,pos);
}

//count function takes head of DLL and returns number of nodes in DLL
int count(node *head)
{
if(head==NULL){
return 0;
}
return count(head->next)+1;
}

//print function takes head and prints the DLL nodes values
void print(node *head){
if(head==NULL){
cout<<"NULL";
return;
}
cout<<head->data<<"->";
print(head->next);
}

//main function implements the above functions
int main()
{
node *head = NULL;
//inserts 10,30,40,20,50 into DLL by calling insert function
insert(head,10,1);
insert(head,30,2);
insert(head,40,3);
insert(head,20,2);
insert(head,50,2);
print(head); //prints the DLL to console
//prints the value returned by count function
cout<<"\nCount of nodes: "<<count(head)<<endl<<endl;
//calls remove function to remove node at position 2.
int val = remove(head,2);
if(val!=-1) //if val is not -1 then node is successfully removed from DLL
cout<<val<<" removed from DLL"<<endl;

print(head);
cout<<"\nCount of nodes: "<<count(head)<<endl;
return 0;
}

//output screenshot

//any query, post in the comment section