Thread: Swap nodes in linked list

hi all, right i am trying to swap two nodes around in a linked list, as part of a sort functions. How while swapping the nodes a round i am tryin to take into account if the nodes been swaped are at the start or end of the linked list, how i have written the following, but its does not work correctly (makes an node within the linked lists disaprear) have you got any ideas whats wrong or do any of you have a function which does what i am looking for that i could have

regards BOAZ

Code:

void swapNodes(pre_rec temp, pre_rec temp1)
{
    pre_rec templeft, tempright;

    templeft = temp->prev;
    tempright = temp1->next;

    temp->next = temp1;
    temp1->prev = temp;

    if (templeft != NULL)
    {
        templeft->next = temp1;
        temp1->prev = templeft;
    }
    else
    {
        temp1->prev = NULL;
    }

    if (tempright != NULL)
    {
        tempright->prev = temp;
        temp->next = tempright;
    }
    else
    {
        temp->next = NULL;
    }
}

Hi,
i have written a small code for this. have a look at it

insert

Code:

void swapNodes(node *p, node *q) {
	printf("\nNode to be swapped p = %d\t q = %d\n", p->val, q->val);
	node *prevP, *prevQ, *temp;
	// check if one of it is head or not

	if(p != head && q != head) {
		for(prevP = head; prevP->next != p; prevP = prevP->next);
		for(prevQ = head; prevQ->next != q; prevQ = prevQ->next);
		prevP->next = q;
		temp = q->next;
		q->next = p->next;
		prevQ->next = p;
		p->next = temp;
	} else {
		prevP = prevQ = NULL;
		if(head == p) {
		       for(prevQ = head; prevQ->next != q; prevQ = prevQ->next);
		       head = q;
       		       prevQ->next = p;
		} else {
		       for(prevP = head; prevP->next != p; prevP = prevP->next);
		       head = p;
       		       prevP->next = q;
		}
		temp = q->next;
		q->next = p->next;
		p->next = temp;
	}
}

Regards,
Sandeep Patra

whats a node ?

A node is like a space in a book shelf - it can hold things. You decide via your program, what that "thing" will be (a struct is common), and you decide via pointers on the link, what shelf and column you want that "thing" to rest upon.

Each node is connected to another node, which makes the term "linked list" a good one.