c++ - understanding how to add new node at end of link list -

struct node {     int data;     node *next; };  //function add node . . . listnode <nodetype> *newptr = getnewnode(value); if( isempty() ) //function check if list empty     firstptr = lastptr = newptr; else {     lastptr->next = newptr; // 1 do?     lastptr = newptr;  // 2 , this? } 

this piece of code textbook. im having hard time understanding 2 lines marked numbers above. understand if list empty point first , last pointer our newly created node. however, if there node in list, how work?

the thing confused me both lines pointed newptr created. difference between line marked 1 , 2?

here take on it.

for 1: telling pointer part of lastptr point new node

for 2: point lastptr newptr? why did point newptr twice?

can please explain?

lastptr->next = newptr; // 1 do

at stage, lastptr points node @ end of list. next member null, because nothing follows after yet. next updated point @ new node because new node follows after previous node, previous node has updated point @ next node in list - new node being inserted.

lastptr = newptr; // 2 , this?

this telling list new node last node in list.