Question

Answers will be given extra reward

Convert the following SINGLYLINKEDLIST code into DOUBLYLINKEDLIST code. Such that

struct Node {

int element;

structNode*next;

structNode*prev;

}

struct Node *head = NULL;

structNode*tail =NULL;

The SINGLYLINKEDLIST code is as follows:

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

struct Node{
int element;
struct Node *next;
};

void get(struct Node *head, int pos)
{
struct Node *temp;
temp = head;
  
if(head == NULL)
{
printf("List is empty!\n");
}
  
for(int i=0; i < pos; i++)
temp = temp->next;
  
printf("The element is %d\n", temp->element);
}

void printList(struct Node *head)
{
struct Node *temp = head;
  
if(head == NULL)
printf("The list is empty\n");
else
{
printf("\nList: ");
  
while(temp != NULL)
{
printf("%d ", temp->element);
temp = temp->next;
}
}
  
}

struct Node * removeElement(struct Node *head, int position)
{
struct Node *temp, *prev;
  
temp = head;
prev = NULL;
  
if(head == NULL)
printf("The list is empty!\n");
else
{
for(int i = 0; i < position; i++)
{
prev = temp;
temp = temp->next;
}
  
prev->next = temp->next;
free(temp);
}
  
return head;
}

struct Node *reverseList(struct Node *head)
{
struct Node *temp, *prev, *next;
  
temp = head;
prev = NULL;
next = NULL;
  
  
while(temp != NULL)
{
next = temp->next;
temp->next = prev;
prev = temp;
temp = next;
}
  
head = prev;
  
return head;
  
}

struct Node * insertLast(struct Node *head, int element)
{
struct Node *newNode, *temp;
  
temp = head;
newNode = (struct Node *) malloc(sizeof(struct Node));
  
newNode->element = element;
newNode->next = NULL;
  
if(head == NULL)
head= newNode;
else
{
while(temp->next != NULL)
temp = temp->next;
  
temp->next = newNode;
}
  
return head;
}

int sizeList(struct Node *head)
{
struct Node *temp = head;
  
int sizeL = 1;
  
if(head == NULL)
return 0;
else
{
while(temp->next != NULL)
{
temp = temp->next;
sizeL++;
}
}
  
return sizeL;;
  
}

int main(int argc, const char * argv[]) {
  
struct Node *head = NULL;
  
head = insertLast(head, 1);
head = insertLast(head, 2);
head = insertLast(head, 3);
head = insertLast(head, 4);
head = insertLast(head, 5);
head = insertLast(head, 6);
  
printList(head);
  
get(head, 2);
  
head = removeElement(head, 2);
printList(head);
  
get(head, 2);
  
printf("\nThe size of the list is %d\n", sizeList(head));
  
head = reverseList(head);
printList(head);
  
return 0;
}

Answer 1

//comment has been added at all the places where the code was modified

#include <stdio.h>

#include <stdlib.h>

struct Node{

int element;

struct Node *next;

struct Node *prev;            //prev was added

};

void get(struct Node *head, int pos)

{

    struct Node *temp;

    temp = head;

    

    if(head == NULL)

    {

        printf("List is empty!\n");

    }

    

    for(int i=0; i < pos; i++)

    temp = temp->next;

    

    printf("The element is %d\n", temp->element);

}

void printList(struct Node *head)

{

    struct Node *temp = head;

    

    if(head == NULL)

    printf("The list is empty\n");

    else

    {

        printf("\nList: ");

        

        while(temp != NULL)

        {

            printf("%d ", temp->element);

            temp = temp->next;

        }

    }

  

}

struct Node * removeElement(struct Node *head, int position)

{

    struct Node *temp, *prev;

    

    temp = head;

    prev = NULL;

    

    if(head == NULL)

    printf("The list is empty!\n");

    else

    {

        for(int i = 0; i < position; i++)

        {

            prev = temp;

            temp = temp->next;

        }

        

        prev->next = temp->next;

        temp->next->prev=prev;           //prev of node which is next to removed node will point to prev(node befor the node which is removed)

        free(temp);

    }

    

    return head;

}

struct Node *reverseList(struct Node *head)

{

    struct Node *temp, *temp1;            

    

    temp = head;

    temp1 = NULL;

    

    

    while(temp != NULL)                    // this code was modified(we are swapping two nodes )

    {

        temp1 = temp->prev;               

        temp->prev = temp->next;

        temp->next = temp1;

        temp = temp->prev;

    }

    

    if(temp1!=NULL)              //checking if list is empty or has only one node

    head = temp1->prev;

    

    return head;

  

}

struct Node * insertLast(struct Node *head, int element)

{

    struct Node *newNode, *temp;

    

    temp = head;

    newNode = (struct Node *) malloc(sizeof(struct Node));

    

    newNode->element = element;

    newNode->next = NULL;

    

    if(head == NULL)

    head= newNode;

    else

    {

        while(temp->next != NULL)

        temp = temp->next;

        

        temp->next = newNode;

        newNode->prev=temp;             //prev of last node will point to second last node

    }

    

    return head;

}

int sizeList(struct Node *head)

{

    struct Node *temp = head;

    

    int sizeL = 1;

    

    if(head == NULL)

    return 0;

    else

    {

        while(temp->next != NULL)

        {

            temp = temp->next;

            sizeL++;

        }

    }   

  

    return sizeL;;

  

}

int main(int argc, const char * argv[]) {

  

struct Node *head = NULL;

  

head = insertLast(head, 1);

head = insertLast(head, 2);

head = insertLast(head, 3);

head = insertLast(head, 4);

head = insertLast(head, 5);

head = insertLast(head, 6);

  

printList(head);

  

get(head, 2);

  

head = removeElement(head, 2);

printList(head);

  

get(head, 2);

  

printf("\nThe size of the list is %d\n", sizeList(head));

  

head = reverseList(head);

printList(head);

  

return 0;

}