problem in adding a node in doubly linklist.

[paeez]

how can i add a node after ith node in a doubly linkedlist?(for example after the third node)

[RedSon]

Why dont you try drawing a diagram of what a doubly linked list looks like. Then try to add a node to that diagram on paper and see how it is done. Then you will know.

[DeMan]

Have you thought about how you would approach the method?
How would you find the position in the list where you would like to add the node?
What information do you need to know about different nodes to complete the operation?
Have you attempted the problem already?

[paeez]

iv written the code for adding a node befor a node containing a certain value(the algorithm is the same),but it seems to have problem..
here is the code:

 void insert_b4_search(int ai,int bj)
    {     node *temp;
        temp = head;
 
    while(temp != NULL && temp-> num != ai)
        {temp = temp -> nxt;
 
        if(temp == NULL){
            cout<<"not found"<<endl;
            }    }
 
    if (temp == head){
        insert_at_first(bj);//call add at first method
            }
    else if(temp == tail){
        insert_to_tail(bj);
                }
    else {     ptr = new node(bj,NULL,NULL);
        ptr->prev = new node(bj, ptr->prev, ptr);
        ptr->prev->prev->next = ptr->prev;
            }
        }
 

[DeMan]

you seem to be creating 2 nodes?

if we are at temp, you want to create a node
thisOne to be (bj, temp->prev, temp) //I assume it's value, before after
then (temp->prev)->next = thisOne
set temp->prev = thisOne.

I'm not sure why you are storing the bj. Assuming this is the index of the node in the list, this value will need to change every insert or delete operation (so really you should go through every otem and change the value.

Rather than rely on indexes, you can step through the array counting how many nodes you pass to arrive at the nth node
(ie node->num is not a good idea)