linked list

[kalar]

I have this code:
[PHP]struct node* BuildWithDummyNode() {
struct node dummy; // Dummy node is temporarily the first node
struct node* tail = &dummy; // Start the tail at the dummy.
// Build the list on dummy.next (aka tail->next)
int i;
dummy.next = NULL;
for (i=1; i<6; i++) {
Push(&(tail->next), i);
tail = tail->next;
}
// The real result list is now in dummy.next
// dummy.next == {1, 2, 3, 4, 5};
return(dummy.next);
}[/PHP]

and this:

[PHP]/*
Takes a list and a data value.
Creates a new link with the given data and pushes
it onto the front of the list.
The list is not passed in by its head pointer.
Instead the list is passed in as a "reference" pointer
to the head pointer -- this allows us
to modify the caller's memory.
*/
void Push(struct node** headRef, int data) {
struct node* newNode = malloc(sizeof(struct node));
newNode->data = data;
newNode->next = *headRef; // The '*' to dereferences back to the real head
*headRef = newNode; // ditto
}
[/PHP]
In the first code line 8, we call the function push with the argument &(tail->next).Next in the push function i can't understand what is happening.
Push function:
line 11 : allocate memory for newnode
line12: we pass the data in the newnode data field
line 13 and 14 is that i don't understand
In line 13 we have newNode->next = *(tail->next); or (*tail)->next ???
and what is happening we set the newNode->next to show where ??(i think tail->next shows to the newNode)
Also line 14 i don;t understand.Please help me.Thanks

[Meetee]

I have this code:
[PHP]struct node* BuildWithDummyNode() {
struct node dummy; // Dummy node is temporarily the first node
struct node* tail = &dummy; // Start the tail at the dummy.
// Build the list on dummy.next (aka tail->next)
int i;
dummy.next = NULL;
for (i=1; i<6; i++) {
Push(&(tail->next), i);
tail = tail->next;
}
// The real result list is now in dummy.next
// dummy.next == {1, 2, 3, 4, 5};
return(dummy.next);
}[/PHP]

and this:

[PHP]/*
Takes a list and a data value.
Creates a new link with the given data and pushes
it onto the front of the list.
The list is not passed in by its head pointer.
Instead the list is passed in as a "reference" pointer
to the head pointer -- this allows us
to modify the caller's memory.
*/
void Push(struct node** headRef, int data) {
struct node* newNode = malloc(sizeof(struct node));
newNode->data = data;
newNode->next = *headRef; // The '*' to dereferences back to the real head
*headRef = newNode; // ditto
}
[/PHP]
In the first code line 8, we call the function push with the argument &(tail->next).Next in the push function i can't understand what is happening.
Push function:
line 11 : allocate memory for newnode
line12: we pass the data in the newnode data field
line 13 and 14 is that i don't understand
In line 13 we have newNode->next = *(tail->next); or (*tail)->next ???
and what is happening we set the newNode->next to show where ??(i think tail->next shows to the newNode)
Also line 14 i don;t understand.Please help me.Thanks

Hi,

Push takes two parameters,
1) Node 2) data
You pass two values in Push function i.e. &(tail->next) and i, it puches new value i in node tail->next.
*headRef will refer to &(tail->next). When you create new node, then line 13 will assign *headRef to new node's next node. And in line 14, now, newNode will be the headNode.

Regards

[kalar]

Hi,

Push takes two parameters,
1) Node 2) data
You pass two values in Push function i.e. &(tail->next) and i, it puches new value i in node tail->next.
*headRef will refer to &(tail->next). When you create new node, then line 13 will assign *headRef to new node's next node. And in line 14, now, newNode will be the headNode.

Regards

I don't understand.There is no headRef (in our example is &(tail->next) ).With this code, we put the new node in the end of list and not in the beggining, if this help.

[Meetee]

I don't understand.There is no headRef (in our example is &(tail->next) ).With this code, we put the new node in the end of list and not in the beggining, if this help.

I have just explained you the lines that you don't understand and what the code reveals. You better read the concept of linked list. Google is the best friend.

Regards

[kalar]

Hi,
And in line 14, now, newNode will be the headNode.

As you say newNode will be the headNode but the newNode should be the last element from the list according to the book ,where i find the code