if(frst==NULL‖i==0){/插在表前 newnode->link= first; if( first- NULL )last=newnode, first= newnode eise ∥/插在表中或末尾 newnode->link=p->link if (p->link=- NULL)last=newnode; p->link=newnode, return 1if ( first == NULL || i == 0 ) { //插在表前 newnode->link = first; if ( first == NULL ) last = newnode; first = newnode; } else { //插在表中或末尾 newnode->link = p->link; if ( p->link == NULL ) last = newnode; p ->link = newnode; } return 1; }