Question

1.Implement recursive and iterative delete functions for linked lists. Node declaration of the linked list is given below.

struct node {

int info;

struct node *next;

};

typedef struct node node;

You can assume that all the nodes in the linked list are distinct and each node appears in the list at most once. Prototype of the functions are given below.

node *delete(node *head, int k)

node *recursivedelete(node *head, int k)

• delete deletes the node with info k from the linked list and returns the new linked list. It returns the linked list without modification if k does not appear in the list.

• recursivedelete is a recursive function that deletes the node with info k from the linked list and returns the new linked list. It returns the linked list without modification if k does not appear in the list. Complete the body of functions. If your functions are correctly implemented, output should be as follows.

Original Lists

List: 15 21 49 92 86 35 93 15 77 86 83 8 List: 15 21 49 92 86 35 93 15 77 86 83 8

After Deleting 8

List: 15 21 49 92 86 35 93 15 77 86 83 List: 15 21 49 92 86 35 93 15 77 86 83

After Deleting 15

List: 21 49 92 86 35 93 15 77 86 83 List: 21 49 92 86 35 93 15 77 86 83

Answer 1

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

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

typedef struct node node;

// these two functions are for testing
node *insert(node *head, int d); // to insert elements
void print(node *head); // to print list

node *delete(node *head, int k);
node *recursivedelete(node *head, int k);

int main()
{
   // building a test list
   node *head = NULL;
   head = insert(head, 8);
   head = insert(head, 83);
   head = insert(head, 86);
   head = insert(head, 77);
   head = insert(head, 15);
   head = insert(head, 93);
   head = insert(head, 35);
   head = insert(head, 86);
   head = insert(head, 92);
   head = insert(head, 49);
   head = insert(head, 21);
   head = insert(head, 15);

   // printing
   printf("Original List\n");
   print(head);

   // deleting 8 iteratively
   head = delete(head, 8);
   // printing list after deleting 8
   printf("\nAfter Deleting 8\n");
   print(head);

   // deleting 15 recursively
   head = recursivedelete(head, 15);
   printf("\nAfter Deleting 15\n");
   print(head);

   return 0;
}

node *insert(node *head, int d)
{
   node *new_node = (node*)malloc(sizeof(node));
   new_node->info = d;
   new_node->next = head;
   head = new_node;
   return head;
}

void print(node *head)
{
   while (head != NULL)
   {
       printf("%d ", head->info);
       head = head->next;
   }
   printf("\n");
}

node *delete(node *head, int k)
{
   node *temp = head;
   node *prev;

   // if data to be deleted is first element
   if (temp != NULL && temp->info == k)
   {
       head = temp->next;
       free(temp);
       return head;
   }

   // else search for data
   while (temp != NULL && temp->info != k)
   {
       prev = temp;
       temp = temp->next;
   }

   // if data to be deleted was not present
   if (temp == NULL)
   {
       return head;
   }

   // else change links
   prev->next = temp->next;
   free(temp);
   return head;
}

node *recursivedelete(node *head, int k)
{
   if (head == NULL) // if data was not found or list is empty
   {
       return NULL;
   }

   if (head->info == k) // if data found
   {
       node *temp = head->next;
       free(head);
       return temp;
   }

   // else
   head->next = recursivedelete(head->next, k);

   return head;
}

OUTPUT