Question

Write a remove(E val) method for DoublyLinkedList class
This method remove the first occurrence of the node that contains the val.
.

Answer 1

Method to remove the first occurrence of node that contain val in doubly linked list is provided below.

void remove(E val) {
   // If head node is null then the list is empty
if(headNode==NULL) {
printf("Empty list");
}
   // If the list is not empty
   // If the head node contain required val
if(headNode->val == val) {
     
   // If there is more than one node
if(headNode->next != NULL) {
      
       // Update the previous link of next node of head node
       headNode->next->previous=NULL;
      
       // Now update the head node
       headNode=headNode->next;
      
}
       // If there is only one node
   else
   {
       // Make head node null
headNode = NULL;
}

}

// If the head node does not contain required value and there is only one node
else if(headNode->val != val && headNode->next == NULL) {
printf("Data not found");
}
   // Otherwise make the head node as curr node
curr = headNode;
  
   // Parse through the list until head node or required node found
while(curr->next != NULL && curr->val != val) {
   // Prev node denote the previous node of curr node
prev = curr;
curr = curr->next;
}
   // Check the curr node has required value
if(curr->val == val) {
   // Update the prev node next
prev->next = prev->next->next;
  
   // If the next of prev node is not null
   if(prev->next!=NULL)
   {
       // Update the previous link of prev node
       prev->next->previous=prev;
   }
   // Otherwise make prev as last node
   else
   {
       last=prev;
   }
  
   // free the curr node
free(curr);
}
// Otherwise val not found
else
printf("Data not found");
}