Linked list tail

[cable]

hello i cannot understand why everytime we add a new entry in list we moving the tail with that way

         l->tail->next=new_entry;
	    	  l->tail=new_entry;

shouldn't we use just one of them
what's the difference that force us to use both lines
l is the basic list and new_entry the new we must add

[bernt]

The first line adds new_entry to your linked list, as per the

we add a new entry in list

part of the routine.

The second line explicitly makes new_entry the new tail of the list by assigning it to l->tail, which satisfies the

we moving the tail

part.

Having a variable l->tail available for use reduces the time complexity of adding an item at the end of the list, from O(n) to O(1) (otherwise one would have to traverse the entire list to find the end).

[AndrewHunter]

Well, it would help for a more complete example; however from the code you introduced I can infer the following:

• L represents your main list
• tail is a pointer of type 'node' (your data).
• The 'l->tail->next' line actually adds your new data(node) to the list
• The 'l->tail' line updates the new end of your list

So in your case both lines of code would be necessary. However it is hard to comment anymore based on the lack of information.

[cable]

wow thanks for your perfect explanation both of you
have a nice day