Data Structures and Algorithm Analysis - Computer Science at ...

Sec. 4.1 Lists 103headcurrtailhead20 23 12 15curr(a)tail20 23 10 12(b)15Figure 4.6 Insertion using a header node, with curr pointing one node head ofthe current element. (a) Linked list before insertion. The current node contains 12.(b) Linked list after inserting the node containing 10.currtailheadFigure 4.7 Initial state of a linked list when using a header node.node like any other, but its value is ignored and it is not considered to be an actualelement of the list. The header node saves coding effort because we no longer needto consider special cases for empty lists or when the current position is at one endof the list. The cost of this simplification is the space for the header node. However,there are space savings due to smaller code size, because statements to handle thespecial cases are omitted. In practice, this reduction in code size typically savesmore space than that required for the header node, depending on the number oflists created. Figure 4.7 shows the state of an initialized or empty list when using aheader node.Figure 4.8 shows the definition for the linked list class, named LList. ClassLList inherits from the abstract list class and thus must implement all of ClassList’s member functions.Implementations for most member functions of the list class are straightforward.However, insert and remove should be studied carefully.Inserting a new element is a three-step process. First, the new list node iscreated and the new element is stored into it. Second, the next field of the newlist node is assigned to point to the current node (the one after the node that currpoints to). Third, the next field of node pointed to by curr is assigned to point tothe newly inserted node. The following line in the insert method of Figure 4.8does all three of these steps.curr.setNext(new Link(it, curr.next()));