Question

How do you remove a value that has occurred multiply times in a doubly linked list , the value is in the front , middle and end of the linked list and is also given as a parameter in your method

Answer 1

Struct Node
{
int data; // represents the data present in the node;
Struct Node * prev; // points to the previous node
Struct Node * next; // points to the next node

}

void deleteDuplicateElements(struct Node *head, int duplicateValue)
{
   if( head == NULL || head->next == NULL) return; // if list is empty  
   struct Node *ptr, *temp;
   ptr = head;
  
   // if duplicate value present in first or middle nodes
   // this loop runs till last but one
   for(; ptr->next != NULL; ptr= ptr->next)
   {
       if(ptr->data == duplicateValue)
       {
           temp = ptr; // temp is the current node now
           ptr = ptr->next; // ptr which was pointing to the current node, now points to the next node
           ptr->prev = temp->prev;
           free(temp); // free the current node having the duplicate value
       }
   }
   if( ptr->data == duplicateValue )   // if the last node has the duplicateValue
   {
    ptr->prev->next = NULL; // make the last but one node the last node of the double linked list
       free(ptr); return;
   }
   else
   return;
}